% and fractions are interchangable, work with whatever is comfertable for you.
http://www.flopturnriver.com/chart_pot_odds.html has a table of all the pot odds you need.

One thing to remember when you count outs is to remember that there are 'tainted' outs that will complete your hand but will complete sombody to a better hand.

For example you hold KsQd on a board of 3h,10h,Jc.
You have 8 outs to complete your hand, but the 2 heart outs may give somebody a flush, so they are tainted.

People usually count tainted outs as 1/2 an out or not counting them at all