Originally Posted by: 053804how do you guys come up with chord progressions when writing a song?

I find it more effective to start with a melody, or melodic idea. After I have a melody, the possibilities for chord progressions practically suggest themselves!

For more on this approach look at these tutorials on music theory, improvizing & targeting chord tones:

http://www.guitartricks.com/tutorial.php?input=876
http://www.guitartricks.com/tutorial.php?input=483
http://www.guitartricks.com/tutorial.php?input=491

http://www.guitartricks.com/tutorial.php?input=166
http://www.guitartricks.com/tutorial.php?input=167
http://www.guitartricks.com/tutorial.php?input=146

http://www.guitartricks.com/tutorial.php?input=644
http://www.guitartricks.com/tutorial.php?input=759

Have fun!