OK, I love answering questions like this =) I play a Protection Paladin myself.
Tanks are very fun to gear. As a tank, you have 2 jobs: Make sure that enemies are only attacking you at all times, and mitigate the damage you receive. Failure to complete either of these means failure as a tank.
Lets start with the spec(Talents) The only Paladin tanking tree is the protection tree, though it is NOT smart to just stack as many protection talents as you can. There are many protection talents that are almost useless for tanking, and there are some retribution talents that will help you greatly. Here is a link to my paladin, this is a very common talent build, and you would do well to copy it =) http://www.wowarmory.com/character-talents.xml?r=Kilrogg&cn=Kodini&group=1
Next we'll talk about professions. Most people said that professions wouldn't matter, and in most cases that is true, however as a tank. You should really consider picking up mining. The reason for this is, as your mining skill increases, you gain a stamina bonus, which increase your Health, and therefore makes you a stronger tank. Also, a good profession to pair with mining is Blacksmithing, as it will allow you to make your own plate/ Mail gear, and you will already have most of the supplies needed from your mining.
You asked about weapons... Ok, now we'll go over what kinda of weapon and gear you will need. as a Protection Paladin, you should always be using a 1 hand weapon(usually a sword or an axe) and a shield. (Avoid using shields with intellect on them, as they are intended for Holy paladins, and Restoration Shamans). For your gear the most important stats are Defense, Stamina, Dodge, Parry, Strength and Block. You should stack these, in that order when you are level 80. (Before level 80 you won't see much dodge, parry or block on the gear, don't worry about it, as they aren't very useful until level 80). Once you hit level 80, your first priority to to get to the defense cap. Which is 535 for Heroic 5 man dungeons, and 540 for level 80 10 and 25 man raids. Being defense capped means bosses will not be able to hit you with a critical strike. Critical strikes are attacks that randomly hit for VERY high amounts of damage, usually 2-4 times what an attack usually hits for. Having the 540 defense cap means you are safe in that regard. You should NEVER go into a level 80 10 or 25 man raid without having the 540 defense rating, as you will get killed very fast and the healers won't be able to save you. In a heroic 5 man dungeon, you MIGHT be able to get away with tanking before you are defense capped, but only if you have a very well geared, and skilled healer.
As a paladin, you should ONLY be wearing plate gear(after level 40) After you are defense capped, you need to stack Stamina to increase your Health. once you are defense capped this is you most important stat, and you should take it over any other stat. The rest of the stats I mentioned, are important and will help you tank more effectively, but you don't need to really look for them on your gear because anything that has defense rating will most likely have a combination of dodge, black and parry as well.
Here is a link to my paladin's gear. look at the stats I have, and try to copy them as best you can..http://www.wowarmory.com/character-sheet.xml?r=Kilrogg&cn=Kodini
This answer was mainly focused on how to be a good tank at level 80. From your question I got the feeling that you are not yet level 80. As you tank dungeons before level 80, you should try to take as much gear that has defense rating as you possibly can, however it won't be a very common stat on lower level gear, in which case you should be aiming for more stamina.
I really hope this helps you, as paladin tanking is very fun and rewarding.