The following points will help you decide whether you need a wow paid leveling guide or not:
1. There are a lot of free leveling guides.
Those usually concentrate on giving tips and advices on specific areas of the game. They are usually on-line sites, that offer information. If you enjoy leveling at your own pace, and you are just looking for a source of knowledge on general leveling tips, you should just save your money, and find one of the many free wow guides out there.
2. If you are not really interested in "pacing out" the leveling experience, but just want to get it over with as soon as possible (for example, if you're leveling an Alt) you might need a paid leveling guide that does a lot more then just give tips.
the problem is choosing the right leveling guide. A lot of paid wow leveling guides are of low quality. By saying low quality we usually refer to the leveling guide being out dated, in terms of knowledge or technology.
3. Being outdated in terms of knowledge.
Being outdated in terms of knowledge means the guide is not updated with all the areas and leveling possibilities. For example, threw the various patches Blizzard changed drastically the XP given from quests. That makes questing a huge favorite over grinding for XP. Some guides are still "Stuck" on outdated grinding methods, while "pure questing" guides tend to forget a good balance of the both is needed, because some quests are just not worth doing in terms of time you need to invest in them comparing to the amount of XP you get from them (Like doing group quests).
4. Being outdated in terms of technology .
Being outdated in terms of technology means that most wow leveling guides are written guides. They usually come in the forms of PDF files, online site or other textual form. That is making the player actually stop playing when he needs certain leveling information in game. That's why more updated wow leveling guides come in the form of in game addon, that can be activated inside the wow application, making all the info accessible in game.
5. Good wow leveling guides are fully automated.
That means that they have a task list that tells you what you should be doing next, and an arrow pointing in game on that direction (Including a dot on your mini- map). Whenever you finish a certain step (like finishing a quest for example) the task list automatically updates, to lead you to the next step.
As you can see, wow leveling guides have a real potential of dramatically cutting down on the leveling process needed to get to level 70, The trick is to know what you are looking for in your wow leveling product.