It's going to God for forgiveness for telling a lie, stealing, lust, and any other sin and you ask Him to forgive you in Jesus name.
Than someone in your life does the same exact thing to you through the same sin that you just ask for forgiveness for- (just like the man who owed money mentioned by FloBe) How can you expect God to freely forgive you if you won't do the same? God says don't let a man be deceived what so ever you so you will reap. In the Bible it says we judge (=unforgiveness) people for the same things we do.
We just need to realize that when we sin against God He feels the same pain, hurt, and betrayal we do when people sin against us.
Guard your heart so unforgiveness will not come in and cause a stony heart and if you have a hard heart let the word of God be the hammer it is to break up the stoney ground so you can receive, and understand the love of God through Jesus blood for the forgiveness of all sin. God wants to give you a new heart so you can walk in His ways.