(Even if I'm local, regular hiker, I was trapped in June 2008 (see photos), so, I'll try to apply my recommendations to myself ...)
Common and known warnings, but could be reinforced in moutains area's:
1- Weather brutal changes
Weather and temperatures in mountains could change very quicly (30min, 1hour) and this could be extremely dangerous without minimum set of basic rules:
- Check the meteo before (city halls, tourism information center, web (see below))
- If you plan for a long hike or treck, start early in the morning (thunderstorms are more frequent the afternoon / evening)
Don't minimize the risk of accidents or of being very late due to the meteo (lost because lack of visibility, verry slippery on the rocks...)
2- Difference of altitude
It looks evident, but when you are aware of a difference of altitude for a hike/treck, don't forget that you're supposed to ... come back yourself, not with emergency services. So, difference of altitude have to be doubled and don't overestimate you physical capacities.
The way down could be difficult and paintfull if not. Have in mind also that your knees are more stressed by the come back.
3- Mobile phones
Don't rely, please, on the mobile phones for alert. Most of the time, there is no network in mountains.
4- The right equipment
Adequate shoes, hat, sunglasses, solar cream, raincoat, pullover, ... and a lot of water
5- Keep someone informed
Hotel, police or Gendarmerie...
http://www.ffme.fr/medical/SECOURS_trousse.php (in French)
http://www.meteofrance.com/FR/montagne (in French)
If you are not a regular hiker or if you don't know the local environment, my recommendation is to use a guide (tourism office centers, city halls)
Not really a warning as such but I would advise people not to go away with people who think it would be fun to walk up the ski slopes instead of skiing down them. We walked up a ski slope just to take a picture overlooking the resort!!
Beware of the danger of avalanges!
Especialy when you want to ski off-piste, but also 'just' skiing on the prepared slopes you should pay attention to the warnings for avalanges.
There are two warning-systems. One is a set of numbers. Warning 1 means no danger, warning 5 is great danger. The other one is with flags. A black flag indicates great danger of avalanges, a black and yellow chekered flag indicates medium danger.
If great danger is indicated don't go outside the opened ski-pistes!
Americans have to keep in mind that French ski resorts are much less conservative than their American counterparts. You can go almost anywhere without getting your ticket pulled. Try to follow a local if you want to go out of bounds.
No nice restaurants, no tourist traps and no sight seeing! Just be aware that there is a lot of snow and when you go off-piste skiing or boarding look for potential avalanche slopes, because they're not funny. I can tell you. Have fun!
Before his arrive the danger was Ulrich..after he was not more ...a danger..only a second !!
In the pic the Ulrich's back (?)