I believe that to pay 10% of ones earnings to “the church” based on biblical instruction is actually going directly against biblical instruction.

Tithing In Context

First Abraham

Gen 14 :16  shows Abraham brought back items which didn't belong to him.  He had the goods of others obtained by war, also known as spoils.

Gen 14:20 shows that Abraham gave this previously unknown priest 10%.  It is implied that the 10% is from the spoils, which are goods obtained through battle.

Gen 14:21-24 shows Abraham gave all of the spoils to others in the end.  Abraham didn't want the king of Sodom to come later and say that all the spoils belonged to him.  Apparently Abraham felt that such a claim could be made.

There is no mention of people interacting with Melchizedek after this point.

Note: The 10% was of people and goods – which may have included money.

An account which contains instructions for how spoils were dispersed by way of command is found in Numbers 31:25-31.  What it said was that those who were soilders involved in obtaining the spoils were to pay 0.2% to the temple.  Those who didn't fight were to pay ten times as much or 2% to the temple.  This command came after the time of Abraham, so he was never bound to it.

It appears that Abraham paid the 10% of the goods because that is how much he wanted to pay, not based on direction from anyone else.

There is no mention of paying 10% within the Abrahamic covenant.

Next Jacob

Gen 28:20-22 shows Jacob making a vow with God.  The problem is that it is a conditional vow.  God has the final say as to whether He will bind Himself to it.  Jacob said that if God would protect him on his journeys, that he, Jacob would give God 10%.  If there were a 10% requirement then Jacob here would be adding to that requirement, which would certainly be a sin.  There is no response from God concerning this vow.

Now Joseph

Gen 47:26 shows that Joseph instituted a law for the pagan Egyptians to pay 20% of their harvest to Pharaoh.  It would be nice if our modern governments were so greedy to limit their collections to 20%.  There is no record of Joseph instructing anyone to pay anything to God.  The 20% helped to fund the pagan Egyptian religion.

On to the Mosaic Law

There is no mention of paying 10% in the book of Exodus.

Lev 27:30-33 shows that 10% of the harvest and counted livestock must be given to God.  If the Hebrew people don't want to pay in physical goods, but rather want to pay in monetary form, they must pay a higher percent, 15%.  Also notice that only the tenth animal is to go to God.  So if the Hebrew animal herder has less than 10 animals of a type they don't have to pay.  If the Hebrew doesn't raise crops or animals they don't have to pay anything.

Deuteronomy 12:8 shows that the way that the Hebrews worshiped God was to change as they changed from being nomadic to living in the land.  For one of the issues which Leviticus never addressed was the logistics of distributing 10% of the harvest and livestock.

Deuteronomy 12:11-12 shows that the Hebrews are to bring their 10% to a predetermined place and enjoy themselves with the tribe of Levi. 

Deuteronomy 12:17-19 shows that the 10% along with the other offerings are to be eaten by the Hebrew household along with those of the tribe of Levi at a predetermined location.

Deuteronomy 12:21 shows that if the predetermined place is too far, the Hebrew can eat the animal at home.

Deuteronomy 14:22-23 reiterates the previous instruction, that the 10% is to be eaten at the predetermined location.

Deuteronomy 14:24-27 shows that the previous instruction of adding a 5% surcharge for transferring the food into money was altered in cases where the predetermined location is too far away to transport large quantities of food.  The Hebrews are now to exchange the goods for precious metals, but they are to exchange the metals back into food upon arrival.

Deuteronomy 14:28-29 shows that every three years the 10% of the harvest is to be stored at the hometown.  This food is to be eaten by foreigners (Gentiles), orphans, widows and local people from the tribe of Levi.

The predetermined location eventually became the temple at Jerusalem.

Leviticus 25:3-7 shows that every seventh year the Hebrew is not to plant crops or take a harvest, but they can pick the food that grows on its own.  All of this food is theirs, none of it is commanded to be given to God.

First Samuel 8:7-20 shows a warning from God to the Hebrews concerning the bad things a human king could do.  It says that he could collect 10% of the harvest and livestock.  God wanted the people to see that these actions by a king would seem oppressive to them.

Nehemiah

Neh 10:30-31 shows the first portion of the Law which the Hebrews state they are returning to.  Verse 31 restates the command to let farmland go fallow every seven years.

Neh 10:32-33 shows that the Hebrews are to give one eighth of an ounce of silver for materials needed to conduct the temple service.  Notice that the 10% is not used for this purpose.

Neh 10:34-37a shows that the Hebrews were to bring wood, firstfruits, flour and other materials for temple service.

Neh 10:37b shows that 10% of the Hebrew harvest was to be brought to the tribe of Levi.

Neh 10:38 shows that a priest must be along with those of the tribe of Levi during the collection.  Not all of those from the tribe of Levi were priests.

Malachi

Malachi 3:8-10 is one of the most quoted set of verses concerning tithing.  I will add to that number.

Will a man rob God? Yet you have robbed Me! But you say, "In what way have we robbed You?' In tithes and offerings.  You are cursed with a curse, For you have robbed Me, Even this whole nation. Bring all the tithes into the storehouse, That there may be food in My house, And try Me now in this," Says the LORD of hosts, "If I will not open for you the windows of heaven And pour out for you such blessing That there will not be room enough to receive it.” [NKJV]

This is an accusation from God to the Hebrews, because they were not putting 10% of their harvest into the giant storehouses located at the temple grounds.  God even says that the 'whole nation' of the Hebrews had robbed Him.  God then tells them that He will bless them greatly if they do store their harvest in the storehouses as commanded.  There are some who make the claim that this is the only time where God permits people to test Him.  This is simply not the case, for God gave the Hebrews many means to test Him as to whether He is truly the Lord or not.  

Exodus 7:1-5, Exodus 7:17 and Exodus 8:22-23 show God setting up a means to prove that He is the Lord.  These were tests that if God had failed, He would not be Lord.  Likewise in Malachi God had set up a test for the Israelites to see that God was truly Lord.

On to the New Testament

Luke 11:42 shows that the Hebraic Pharisees were indeed to tithe on their herbs, as their herbs could be counted as a part of the harvest.  Of course the main thrust of the verse was the much more important matter of the lost love of the Pharisees.

While the firstfruits are not tithes, there are some who falsely use scriptures which are about firstfruits to bolster their arguments for the need to tithe.  2 Timothy 2:7 shows that the one who works the field should be the one to get the firstfruits, not the priesthood.

Matthew 25:34-40 shows how anyone can give to our Lord Christ, by helping those around us who are in need.

Heb 7:4-7 is a summary of what the Old Testament teaches regarding the giving of 10%.  Abraham gave 10% of the spoils he took to Melchizedek and the Hebrews were required to give 10% of the harvest to the tribe of Levi.

Heb 7:8-10 shows that the 10% given to Melchizedek was different than the 10% given to the tribe of Levi.  For it says that Levi figuratively gave 10% to Melchizedek.

Conclusion

The biblical way to tithe is for a Hebrew to share one tenth of their harvest and livestock with those who are Levites, foreigners, widows and orphans.  The food is to be consumed at the temple in Jerusalem three times a year in years 1, 2, 4 and 5.  In these years it is to be eaten by the person who raised the one tenth and by the Levites at the temple.  In years 3 and 6 the one tenth is to be eaten by the Levites, foreigners, widows and orphans who live locally.  On year 7 there is to be no tithe.

Since there is no temple today there is no way for the tithing system to function on years 1, 2, 4 and 5.  Since there is no formally recognized Levitical tribe today, there is no way to fully feed them on years 3 and 6.  One can feed the foreigners, widows and orphans to carry out the command, but one must be a Hebrew to do this.  There is no need to worry about the seventh year, unless you are a Hebrew farmer, who would need to let his fields go fallow.

I am not Hebrew.  I am mainly of German descent.  I do not tithe.  If you try to tithe by paying 10% of your income, you will go against the Law as stated.  It would be a transgression of the Law.  It would be a sin.

It is acceptable to give as you please to those who are “the church” as they are often working to do the very loving acts which you wish to be done.  They are often preaching the Gospel, which is an act of love.  Beware, for not all churches use their gifts wisely or honestly.  If they are appealing to tithe commandments from the bible, they are twisting scripture for their own gain.  This demonstrates a critical problem in their ethic, which in time propagates through other areas of how that church will deal with ethical issues.

If you desire to worship God by giving to Him, you can follow the words of The Word, and give to those in need.  One can give in money, resources, time or all of the above.  The key to any such giving is that it is given out of a desire to truly care for that person's well being, and that it be done for the glory of God.  This is how to give to God.