I am no passing expert but I think I can at least offer some basic tips to up your completion percentage and help you cut down on some of the interceptions. Are you playing against the CPU or against users? Also, what kind of passes do you tend to throw? Are we talking a lot of 3rd and long?
One thing I like to do early in games is go for shorter completions and some screens to get your QB's confidence up. If you are trying to sling it around the yard from the beginning that is more hit or miss. What team and playbook are you using?
In terms of interceptions, try and figure out pre-snap based on where the cornerbacks are lined up if you are facing zone or man. Corner routes, deep comebacks and crossing routes can work well against man. Crossing routes, ins and streaks work better to beat zone if you time it right. If you can run the ball successfully then play action can open some opportunities also.
Mix up your play calls, flip plays, etc and see if those help too.