Talk to your family, friends and work colleagues. Tell them about your hobby of metal detecting and of your interest in history and ask them if they know of anyone who has any land that you could detect on. Some land could come your way from someone who knows someone who has land.
You could put up a card in a shop window, in a newspaper or anywhere you think a farmer/landowner may see it.
Some detectorists telephone landowners, email, or send a letter asking for permissions.
The most tried and tested and most popular way to get a permission is to walk up the driveway and knock on the door. This way the landowner can see you face to face and can make a judgement on you.
Dress smart and casual and be yourself. Act in a positive non intimidating way.
Do it alone as two or three men asking one landowner will most likely intimidate him/her. More so if its an elderly person.
Go in the daylight hours.
Make sure you have insurance and tell the landowner so.
Prepare a business card as your details will be on there and makes you look genuine.
If you get a no, be polite and thank the landowner for his time and move onto the next one.
The more farmers/landowners you ask the more one is likely to say yes.
Once you have a permission sort out the details right at the beginning regarding finds.
Most common is a 50/50 split on any treasure trove found.
Its good manners to show the landowner the finds you make. if they take a fancy to one of your finds, let them have it as a goodwill gesture for letting you on their land. This will make the landowner more confident in you and could lead to more land.
At Christmas take them a bottle of their favouite plonk or a box of chocolates. Some detectorists make up a finds case and present them with it.
You will get a lot more landowners saying no then you will yes. Don't get disheartened, its the same for us all.
Keep at it, be determined and before long you will have lots of land, its just getting your feet in the door so to speak.