What should I do when I get disoriented or lost? How can I find help or make myself easier to find?
This is a general question to do when lost in the wilderness, whether it is a meadow or mountain.
If you can no longer see any trail signs, the best thing to do is go back the way you came until you find one and start searching in a circle from there. Never continue to go further assuming there is going to be a sign just up ahead. You may be right, however the risk of getting lost and something unfortunate happening is too great.
If you become separated or lost, many experts suggest staying put (assuming someone knows you were out there). To help make yourself found, you should make unnatural patterns (straight lines or circles) in contrasting colors (rocks, dirt, debris). Making color contrasting flags provides good source of unnatural color and movement. A universal distress signal is 3 flags or 3 triangles.
If you determine your best course of action is to move on, always leave some signal to indicate the direction your are headed. That way if someone finds where you were, they know the direction to look for you in.
It goes without saying that you should always let someone know where you are going and when to expect to hear from you. Also, give them a 'I will call you by this time' time so if you don't, they know they should alert authorities that you may be lost.
I would not recommend staying and hoping that others find you. Except you have a cell phone or another communication device to report that you're lost. Or of course if you can't move because you're injured. If any of this is the case you should set up a signalling fire which should generate a huge amount of smoke (burning damp fir branches is a good start). Start to send Morse code with the smoke and/or light of a torch.
If you are able to move, you generally should. Get your bearings standing on a higher place or getting up a tree. If you can't make out any signs of civilization, look out for rivers or streams. Head for those streams and follow them downwards. It is highly likely that you will find civilization downstream. This rule applies to the parts of the world where rivers don't end up dry. In deserted areas it is mostly the other way around as settlements are established around the source of water.
Btw, if you see help approaches make your self visible and then stand like a Y with your body to signal that you need help.
If you're completely lost but not in an emergency that requires immediate action you should stay where you are to 1) not getting even more lost 2) not getting into dangerous situations.
For example if you're in the mountains and you have no idea where to go to reach you're goal it isn't a good idea to just randomly walk into one direction. The reason for that is: you can get even more lost and more important you can get into dangerous situations. If you don't know the terrain it can be that you're suddenly standing on top of a high cliff and can't find a way back. So I would suggest to stay where you are, try to stay calm. There is the chance that others can find you or that you remember suddenly where you have came from or that the situation that has lead to your looseness (e.g. thick fog) will improve.
If it is an emergency that requires immediate action, I wouldn't recommend to stay, but to try you're best guest and heading into the next civilized area. In the mountains it is always a good idea to generally go down or to follow a small river, creek, or ditch, or something similar. This will often lead you to roads or houses (sooner or later).
I don't think there can be a definitive general answer as you will need to assess the situation depending on the level of emergency, the dangers around you and the likelihood and ease of rescue.
You can make yourself easier to find by making yourself more visible or audible. Again it will depend on your situation but you might have with you a light, flares, clothing that stands out from your environment, a mirror that could be used for signalling, a whistle. Of course the absolute easiest way to get yourself found is to have a mobile phone with signal and an accurate GPS co-ordinate.
If you are worried about becoming lost you should spend your time improving your navigation skills with a map and compass and make sure that you have those tools any time that becoming lost is a possibility.