Point of view is a tricky thing to get right, and it takes a lot of practice. As a general rule, you should be inside only one character’s head per scene, and you should make it crystal clear to the reader which character that is. While you’re inside that character’s head, only what he or she can directly observe should get reported to the reader (therefore, no seeing what’s around corners that your character can’t poke his or her head around.) Also, any commentary on the action should be filtered through the viewpoint character’s perceptions and attitude.
First person, and single-viewpoint tight third person, are good points of view to use when part of the impact of your story depends upon keeping some plot elements secret from both your POV character and the reader until the time is ripe for them to be revealed. Try to avoid writing yourself into plot situations where your first person narrator knows something that the reader doesn’t; it’s a tour de force if you can pull it off, but the failure mode isn’t pretty, and even a successful attempt is going to leave a certain number of resentful readers in its wake.
True omniscient point of view is fiendishly difficult to do well, and it’s a good idea to master multiple-viewpoint third-person first. The longer the novel, and the more ground it covers, the more point of view characters you may need — but when in doubt, err on the side of parsimony.