A few pointers...
1. Just because you filed a route doesn't mean you'll get it. ATC has many reason for giving you a new route. (Expect the unexpected)
2. Call for your IFR clearance before you set up your Nav radios and/or GPS.
3. Set up those radios before you take off. It's a bitch to do it shortly after take off an mostly likely it will get screwed up.
4. Follow your clearance. If ATC say's intercept V97 and you intercept V63 you may end up with a violation or, if you're in the mountains, an impact with cumulus granite.
5. Think ahead of the aircraft. Never let the airplane get to a place your mind hasn't already been thinking about. Ask yourself, what are my next two things. Or if your situational awareness is lagging behind, ask yourself, "where am I?", "where am I going?" and "how do I get there?"