First of all, I must admit I'm not a big fan of guides for playing games, as I'm quite reluctant to being told what to do and how to play, after all, let's not forget that we're supposed to have fun through the whole game, and not just after hitting a certain level or aquiring a certain item and so on. I like reading some of the guides, though, as now and then I do find some good tips or an interesting point of view. There are guides to power leveling, to making gold (most of them) from grinding or different professions and not least, guides to instances and their bosses. The thing that nobody's saying is that Blizzard is in fact continously trying to balance the whole game in respect to gold, experience and whatnot, so almost every activity you might end up doing in the game, except chatting and fishing, I suppose, leads your character ro getting gold and experience.
Oh, And dying makes a good exception too ;). Another important aspect, which concerns mostly the gold making guides, is the differences in servers' economies, if the guide advices taking skinning as a major source of profit and the server tour character's on is loaded with skinners, that wouldn't work so good, right? Or if Blackfathom Deeps is an instance that gets visited once in a full moon on your server and the guide advices creeping it for experience over and over again, it's most likely you's be doing it alone or at all. I guess the best thing to do is go with the game's flow until about level 20, concerning both exp. and money, just commplete
the quests, talk to the npcs - this usually leads to crossing the boundries between regions, make friends, enjoy the game :)
Then it might be a different story and depending on one's highlight -high experience? lots of gold? both medium? - the path to take can vary a little. A powerleveling approach demands skipping the quests that are demanding a lot of traveling or instances that you can't complete, because you don't have a guild, or enough friends online, or you simply hate it - like me with the above mentioned BFD. It's better in this case to just leave those be and stick with the quests bases mainly on grinding, the "get me x lions paws" type or "kill y mobs and return to me" - these are even better, they don't require a lot of space in the bags always too small. So this way it's not just grinding, but some money from the npc (either cash or an item that can be vendored) and bonus experience upon completion. Of course, the higher the level, the difficult it is to get to the next level or to the next region with more quests of this types. But if you find yourself with all easily doable quests done and still an experience gap to fill until the next thing, grind away if it doesn't bother you. I usually like shooting more rabbits with one bullet, but sometimes it just can't be done, or the time required would be just too long compared with that for the grinding, so then I go for that.
I'm finding myself giving advices just as a 'regular guide', but I'll say this one more time: don't do anything that takes away the pleasure to play. If you hate grinding, but think it's "better for the character", don't do it; it's supposed to be fun, remember? That's what games are for. That is, of course, if you're not a professional farmer... If you hate PUGs, don't team for instances, just leave those quests away. Or get into a nice guild. If you can't find anything to like, why play the game in the first place? Or if you only find it rewarding to hang out with friends, try the *free* chatting programs and don't pay a monthly fee just for that.
A good guide that spells out the basics od powerleveling is freewarcraftguides.com, as for the money part, there's just to much to say and too many strategies, but just like in real life, there's always the basic rule of market economy, the offer and demand are very important on the AH and usually just vendoring items is not going to bring a pile of gold.
The last thing to note would be the add-ons that many people use and are accepted - not the abusing ones that would eventually get your account banned. I haven't use any so far, mostly out of laziness I think, but because I don't enjoy using them either. But if you feel you could use some automated help for AH scanning, for fighting, for groups and so on, try them.
Have fun and remember that there's life after Wow ;)