Most new writers misunderstand Third Person. Modern Third Person is not the Omniscient Narrator - as used by Jane Austen - able to see everything, everywhere, as if the author was a movie camera, and even able to hop outside the story to talk directly to the reader. Very few authors write like that any more because today's reader wants to get inside the heads of the characters. Readers want to identify very closely with the hero or heroine - to become the character - and they can't do that if they're standing outside, looking in!
Of course, you can achieve that easily in First Person - pick a character, and make him or her tell the story. But there's a snag - you can only write what that character sees. If your First Person character isn't at an incident, your only option is to have another character tell them what happened, which is far less engaging for your reader than describing it first-hand. Your First Person character also doesn't know what other characters are thinking or feeling.
By using Third Person Subjective and swapping your POV (point of view) from one character to another, you can cover all the action, plus include a range of other characters' emotions and reactions. Strangely, this can actually increase suspense, because you can let readers know facts unknown to your main protagonist - for instance, that the 'friend" who's being so helpful is actually plotting against them...
The critical thing when using Third Person Subjective is that the reader must always know who's telling the story. That's easier if you limit the number of POV's. Two may be enough (your hero and heroine). Any more than three or four, and the reader's going to lose track! Be careful not to switch too often, too. For instance, say you're writing a scene between two lovers. You're telling the story from the woman's POV and you suddenly feel the reader needs to know what HE is thinking - so you switch into his POV. Oh, but now you need to show HER feelings - so you switch again, and so on. To the reader, this is like watching a tennis match - it's hard to keep your eye on the ball!
When you're starting out, limit yourself to one POV per scene. By doing this, you force yourself to ask - "did I choose the right person for this scene?" and, "How can I convey the other person's reactions without switching?". That way, you'll learn how to choose the right POV, and discover ways to hint at a character's feelings by their movements or dialogue. Once you've gained confidence, you can allow yourself to change POV once - but only once! - in each scene. Some experienced authors do break that rule and get away with it: however if you're tempted to switch more often, you need to be sure you've examined your reasons for doing so, and that it's the best way (not just the laziest way) to achieve your goal.
Used well, Third Person Subjective can really enrich your novel, imbuing it with all the thoughts and emotions of your characters and making them very real to your reader. It takes practice, but it is worth it!