anyone know what would be good? ive been told that tailoring is good but i dunno what else

Tailoring may be smartt because yopu can make some of your own cloth gear. Especially at lvl 70 it is usefull when you can make your Primal Mooncloth (PMC) set or for SP's a spellcloth set. Both are BoP, so you will have to make them yourelf.

As second profession I suggest you go for a gathering profession: that will generate some money for you. I personally did like skinning. But herbalism of mining may also be an option. Search this forum for more info on this subject...

As mentioned already, Tailoring is probably the single best profession for a Priest, the PMC and FSW sets are both excellent for Holy and Shadow priests, respectively, particularly with consideration for how easy they are to get.

Enchanting is nice.  I have this one, which is good because I'm often the only enchanter in a 5-man which means we can get shards and such.  As for the personal benefit, all you really get are the ring enchants which are nice (a total of 40 +Healing or 24 +Damage), but not something to go gaga over.  Still, like tailoring, it doesn't require another gathering and/or crafting profession to make it useful.

Alchemy is nice because potions, elixirs, and flasks can get expensive.  Of course, you can buy all of that, but what Alchemy really gets you is the trinket, which is very good because it increases the value of heal potions (which, if you chain chug mana potions, makes it worth as much as 40 MP5), not to mention the +15 all stats or the new one with +119 Healing.

Engineering isn't particularly good, because most of the gadgets you'd make don't have any real synergy with healing or casting.  OTOH, the healing lens you can make is fantastic, but is it really worth a profession just for one piece of gear?

Jewelcrafting is another one but, again, probably not particularly useful.  You can make some nice money with it, and get some decent trinkets.

You could always get a gathering profession, but I'd also recommend against this.  If you don't have a crafting profession to make use of it, you're really just farming.  If you're going to do that, I'm not sure it's worth it, because you can probably make just as much money doing dailies in the same amount of time, now that 2.4 is live.

So, IMO, the best profession combinations are probably something like tailoring/enchanting, or tailoring/alchemy.  YMMV

In case of lvl 70 or alt characters I do agree with the above posting.

However when this is your first and main character, I would tend to go for a farming profession as 2nd one. Enchanting will only generate some gold at higher levels. And the dailies are in most cases lvl 70 onlu.

This isn't really specd 4 a priest but I, being a level 20 priest can make 6g like that!!!
I recommend enchanting and tailoring

Tailoring and Enchanting are the best professions for prisets i think.