I'll probably repeat some of what the others said, but I'll answer your questions again anyway
Is there any servers you recommend i join?
All public servers require to meet strict criteria to get a server license - that ensures that every server has the same game rules, respawn times etc. It also helps with making sure that the gameplay is good on all public servers. Some are better than others obviously - Tactical Gamer being the most loved one by many people, although that one's in the states. PRTA recently also getting a very good reputation. NwA and UK Warfare are also good choices for UK-based servers.
How does the ranking system work?
Not

All there is is a commander (not always sadly), and squad leaders - but you require no rank or anything to take these roles.
Can anyone get in a jet for example and fly it around, because thats stupid if they can.
As the others have stated, no. Firstly a pilot kit is required (which includes no proper weaponry, so if you are a pilot, you won't be able to change your mind and jump out to engage the enemy, and more importantly, most servers clearly state that noone who did not practice at first is allowed to use any aircraft. This is also important to you: Stay away from heavy vehicles and anything that flies until you had some experience as infantry man (to see how these vehicles operate from a different perspective) and trained using the vehicles on an empty LAN or a co-op server.
Is there anything i should be aware of?
A lot of things - most of which are in the manual.
When you join a game, look for infantry-squads, named "Teamwork", "VOIP" etc, "INF TW", "INF VOIP" etc. Join them, tell the squad leader you are new, and unless you are unlucky with the squadleader, he'll help you out and answer your questions. Do not spawn with any specialised kits without asking (default is rifleman, medic is also normally no problem).
How does Squads work?
It's important to know that without being in a squad, nothing works. As for the squads themselves, you simply join one that you think will fill the role on the battlefield that you like - at first this should be infantry, just because it's not that much of a responsibility and you won't get yelled at for wasting a helicopter due to inexperienced flying. But don't worry, as soon as you know a couple of people and got used to the game, you can move on to the heavier assets. But due to their high respawn times and the tickets attached to them (losing one instantly makes your team lose several tickets - and if they reach zero, the match is lost, obviously), you should at first probably not man aircraft or tanks.
Also, please do not use smaller vehicles as one-way taxis. Get transported in a friendly APC (that's what they're there for; a good squad leader in your squad will make sure you get transproted by an APC or helicopter), or take a truck/jeep - but in that case, bring it back to safety after doing your mission. Don't leave it in the middle of the battefield. Take it with you as if it was another squad member.
Do i have to take orders from higher ranks?
No - there is no ranks, after all. You should listen to your squad leader though.
Is there some thing i should not do?
Too many to name them all
How does training servers work?
Currently, the training mode does not exist in PR. There are co-op servers that you can use to train a bit, and you can create an empty LAN server to get used to assets. Some clans also have passworded training servers up, but I don't know much about those.
Do i have to train before i join a server?
Read the manual and try out the different weapons and pieces of equipment in an empty LAN server if you want to be sure not to make a mistake. But generally, you don't need to train, unless you intend to fly etc.
Do i start with a certain weapon?
Depends on your kit, obviously. Mostly, you'll have the same primary weapon for almost every kit in an army (as in, the US Army will almost always give you an M4, unless you are, for example, a machine gunner).
What happens when you die? Do you respawn with a new life? NLR?
You respawn at the main base, a friendly forward outpost (those can be built by your team - read the manual for detailed information) or your squads rally point (your squad leader can place those every now and then for a short time). Vehicles respawn in the main base, usually. Respawn times are high though.
Also, when you are shot, you normally are not instantly dead, but you are wounded. For up to five minutes (you can skip that, see manual), a medic can revive you on the spot - that takes a while though and should not be done under fire.
What about roleplay?
Most people do not roleplay. The feeling is great even without, though
Do i have to use my Microphone?
Short answer - yes. Long answer - no, but it helps a lot. Seeing how you're british, your english probably is good and you should not have issues communicating, so I'd suggest using it.
i understand there will be annoying people and trolls on the forum as-well as nice people who can help me. So please dont flame me.
I hope we could disappoint you there

Welcome to the forums, and enjoy the game!