Many people will start with a hunter character. Because it is easy to level and to tame a pet, which will help him fight for as you play the game. there are 5 tips for hunter below, which can help you in your quest to get to a level 70. This is the top level.
You spend the training points via the 'Beast Training' button/spell on the general page of your spellbook (P). You can learn abilities to train your pet with from the Pet Trainer (usually located in most cities near the Hunter Trainer), or from other pets. To learn an ability from the Pet Trainer (Growl, +stamina, +armor, +resistances ) it just costs money and the ability gets added to your 'Beast Training' list. To learn an ability from a pet (which you can then train to other pets, unless it is species prohibitive (only Boars get gore, etc.)) the pet simply has to use the ability repeatedly. After a while (time varies, you might get the ability right away or it may take a good couple hours of combat) the ability will get added to your 'Beast Training' list and you can then teach it to other pets it is available to.