There are a lot of things that are easy to miss on an instrument flight...

1) Operating Below MDA

It's one of the leading causes of accidents on instrument approaches. If you're flying a non-precision approach, check (and re-check) your MDA altitude. And remember, you need to see at least one of these 10 things before you can descend below MDA to the runway.

2) Inspections

In addition to having the pitot/static system and transponder checked every 24 calendar months, you need to check your VOR(s) in the preceding 30 days if you plan to use them.

3) Regaining Currency

If you regain currency with FTDs or ATDs in addition to an aircraft, the requirements to regain instrument currency change. Make sure you read FAR 61.57(c) before you go.

4) Cold Weather Corrections

In cold regions of the country, instrument approaches require cold weather corrections. It's your responsibility to make sure you know how to correct the altitudes, and which segments of the approach need to be corrected.

5) Filing Direct

If you file a direct route and you're crossing an ARTCC boundary, you'll need a waypoint on your route within 200 miles of the boundary.

6) Inoperative Equipment

The acronym "GRABCARD" helps you remember required equipment for IFR operations. Equipment as simple as a clock must be installed in the aircraft and can't be substituted by an external one.

7) Required reports to ATC

Whether it's reaching VFR-on-top or not being able to climb/descend at least 500 FPM, there's a list of reports ATC expects you to make. The full list can be found in AIM 5-3-3.