Another simple one to remember is how to calculate track miles to run.
Say you are tracking to a position to intercept an ILS. Or you are being vectored by air traffic.
You are tracking/being vectored towards this position at an intercept heading to then intercept and fly the localiser. You are taking a DME read out from the ILS facility but because you are flying at an intercept heading before then flying staight to the facility you know your actual track miles is longer.
To work out the track miles to run just remember these 3 values.
30 degrees .9
60 degrees .75
90 degrees .5
For example
The runway and therefore ILS is 090 degrees for runway 09.
You are flying on a heading of 180 degrees to the 10 mile fix. Your DME read out on the 180 hdg is 10 miles. However you are slightly north west of the runway at this stage and not tracking directly to the runway you are going to intercet the 090 QDM at the 10 mile fix. A 180 hdg is a 90 degree intercept. 90 degree equals .5. If 10 mile dme is .5 you must double this to make 1. Eg the track miles to run is 20 miles.
Similarly a 60 degree intercept equals .75. So a 10 mile dme reading would mean you are 13.3 miles to run.
30 degree intercept equals .9. Therefore with 10 mile dme equals 11.1 miles.
Try this. I think the values I have used are pretty acurate but there may be some more scientificly minded people out there whom can correct me. I find the above has worked well for me as a rule of thumb when calculating descent profiles.