Diversion aerodromes is a personal preference. Here are my considerations...
I'll always have one alternate that's near to my destination which you might call a 'crash div' or whatever. It's purpose is to be there if some unlucky sod ploughs the runway at the destination and it can't be hoovered up before the fuel endurance approaches. Let's be honest if it'll only take 15-20 mins to clear up whatever is obstructing the runway, I'd rather do a few orbits/GH and get in to where I'm supposed to be going than divert elsewhere. This div is plogged properly.
I'll always have an en route diversion too. Simply just in case something goes wrong at altitude and I know where I'm going to try to land. I wouldn't book it as a diversion, it'd be a bloody emergency - I'm landing! Likewise I wouldn't have this one plogged either, just a knowledge of where it/they is/are from my track.
A weather diversion always seems to me to be too cowboy like. The short trips that most PPLs do arn't long enough for the weather to become 'unexpected'. I concede that on longer international and transcontinental flights, how much you trust the weather man is down to your judgement alone. I'd have a good planned weather div for these types of flight. But as before, for a PPL in the UK if the weather is pants, turn back and return to whence you came! Or back to where you didn't continue into the poor weather in the first place. This is very IFR capability determined.
In selecting a div I look for general weather (VFR if possible) and more importantly the wind direction and strength. I wouldn't be comfortable having a planned alternate where the wind strength would be at the 'demonstrated crosswind limit', sods law says it'll be outside of the limit and I'd break something. At the same time as reasoning with the weather I consider runway length, but only in so much as, is it long enough. And I mean long
enough, no adding extra length for whatever silly reason. We learn PFLs, flapless, glides, and short field techniques for a reason, and any strip with an ATZ is likely to have at least 600m grass (which is fine for most if not all singles, and many twins in most weather conditions that GA tend to fly in).
After the weather and wind, I don't really care what facilities are available! Yes a cuppa and some avgas might be nice, but then most airfields that make sensible diversions have these facilities anyway. In my mind, a diversion is an emergency situation for whatever the reason, be it you, or someone else at your original destination. Of course if a narky hass-hole says you cannot divert because you've not booked an aerodrome "Pan-Pan short of fuel" would probably work just nicely!
