Hi Nick, well first you need to familiarise yourself with the treasure act so you'll know exactly what constitutes as treasure. Obviously if it's a single item then it will probably be out of the ground before you realise, if on the other hand it turns out to be a hoard then it's best practice to call the FLO immediately and they will tell you if they can get someone there to excavate it (don't worry it's all yours and the landowners) If they can't get there that day then cover it up.
Now it doesn't matter whether you put a tent on it, park on it, buy a shot gun and guard it lol but the possible information that can be gained by proper excavation and recording is valuable to the historical record.
There are many examples on here of the right way of doing it but here's one which shows what else can be discovered other than a hand full of coins;
http://www.detectingwales.com/index.php?topic=16219.0So your first point of contact should be Mark Lodwick on 2920 573226
Now sometimes you've got more chance finding a hoard than you have contacting the FLO lol so my advice would be to phone Swansea Museum if you get no luck.