Just to add slightly to the previous posts. I find the easiest way to work out an entry to a hold is to assume the fix as the center of your DG/HSI and then visualise the holding pattern according to that.
The most important thing to then is to ensure you place the holding pattern on the correct radial and to remember the direction of the turns. With the pattern visualised right in front of you, it is easy to see what entry procedure is required.
With a bit of practice 'hangar flying' this it becomes a really quick and easy way to work out entries. I read some more explaination of this technique somewhere in a flying magazine, if i can find it i'll add to the post at a later date.
I also use the T's theory! Although i have heard many many variations on it. Mine is:
Time, Turn, Throttle, Tune , Talk, Trim
(similar to above i know) reciting each of these at each stage (or fix on an IAP) seems to work well to ensure correct instrument procedures.
As for timings etc i agree with Tinstaafl, just a bit of common sense on the variations based on known winds is a good way to get started, without having to remember specific formulae and keeping 'heads down' in the cockpit. (N.B. I'm not suggesting that you should disregard the wind correction formula, there is just a time and a place especially with a pop up clearance).
Lastly, on some radios i have used you can select 'current radial' from a VOR which allows you to quickly see on a digital display your current radial. This is great for working out abeam positions and for other situational awareness. Off the top of my head i think this was a funciton on the older collins radios.
Just my 2 pence worth!
JG