How do keep from going to church?

Going to church is an expression of faith that also has important cultural and traditional implications. If you avoid going to church, then you put your faith, along with value in culture and tradition, up for questioning. Thus the best way to excuse yourself from church services would be to make sure everyone involved is aware of where you stand in terms of faith, culture and tradition. This could be achieved through volunteer work, community work, or evangelism, among other options. You could also just lose faith, which would be an understandable reason for not going to church.
In the short term, there are many options; feigning illness, claiming to be busy, needing to go somewhere. Basically any excuse for not going to work will be fine for not going to church. In the long term though, you will need to adopt some of the strategies from the first paragraph.