When playing close to the table, you have very little time to make a transition from forehand to backhand shots, and vice versa. If you are playing a relatively quick backhand or in a fast rally, there's no need to go into a backhand stance for this shot. Therefore, learn to play this shot from a slight forehand stance, with the right leg (for right-handers) slightly back. That way you'll be able to make a quicker transition both to the backhand and to the forehand. (You should still rotate the body to the left, allowing you to still play a strong backhand.) It's only when you have more time to play a more powerful backhand (in a slower rally or from further off the table) that you might want to stand more neutral, or even (when you have time) in a backhand stance. Note that even in this slightly forehand stance, if you are facing crosscourt (i.e. crosscourt to the opponent's backhand, assuming both are righties), then you are essentially in a neutral stance anyway, with your body perpendicular to that crosscourt line.

There have been numerous discussions over the years over what is the most important part of table tennis. Many say the serve, or receive, or the forehand, or footwork, or consistency, or tactics, or mental strength, and so on. Of course, many of these discussions are like arguing which link in a chain is most important! Also, many of the aspects are related. For example, having a good forehand isn't so helpful if you don't have serves, receives, footwork, and tactics to get that forehand into play.  

Here are the seven links of table tennis that pretty much covers it all. Note that things like tactics, mental strength, footwork, etc., are all parts of these, but spread over multiple parts. One strength or weakness can lead to strengths or weaknesses in multiple links.

1. Serve. Every point starts with it. Many call it the most important aspect, often the least practiced. It's primary purpose is to set up the best part of your game, usually some sort of attack.
2. Receive. Perhaps the weakest part of most player's games. How often do you really practice it, other than in actual games? The receive can focus on consistency (so make few mistakes, but often give the server the initiative); neutrality (make a few more mistakes, but get into a neutral rally); or aggressive (make more mistakes, but take the initiative). You should be able to do all three of these.
3. Pushing. How many rallies start, usually until someone finds a ball to effectively attack. They can be both long or short pushes.
4. First attack. Both players should be looking for this, even defensive players if the opponent doesn't force the attack. The key is the first attack has to be both consistent and effective, and well-placed.
5. Defense or Counter-Attack. How you handle the opponent's attack. Blocking is the most common method, but also soft counterlooping, fishing, lobbing, and chopping. Or you can deal with the opponent's attack by counter-attacking with aggressive blocks, counter-hits, or counterloops. Many up-and-coming players develop strong attacks but fall apart when the opponent attacks first. If you want to be good, you need to be comfortable whether you or your opponent attacks first.  
6. Continued attack. How you continue your attack after the first one, often against an opponent's block. Consistency and placement are key until you get the right one to end the point.
7. Putaways. Ending the point!!! Smashes and loop-kills.

So, how strong are you in each of these links? A chain is only as strong as its weakest link! (That's not technically true in table tennis, of course - a player may get away without a strong putaway, for example, if he has a strong continued attack. But if you are weak in any of the above, it weakens your game.)

Especially when looping, you need a loose arm to maximize power. Many players literally jerk their arm backwards when looping. Instead, relax it into a natural backswing position, and then use the natural elasticity of the muscles to slingshot your arm into your forward swing. Think of your arm as a rubber whip and whip it into the ball with smooth acceleration. You should extend this thinking to the entire body since looping is a full-body shot - with power coming from the legs, hips, waist, shoulder, arm, and wrist - all part of one big whip that smoothly accelerates into the shot. Watch the top players and do what they do!!!

It's often difficult to judge how much spin you are putting on the ball when you practice serves. Without this feedback, it's not easy to improve your serves. So try this - find a large, carpeted room, and practice serving there. Spin the ball as if you were serving and try to control what it does on the rug. With backspin, make it roll back to you. With sidespin, make it curve sideways, perhaps aiming at targets. (Perhaps have a little fun by having it curve around objects.) Keep working on getting more and more spin, while still controlling it. To maximize the spin, accelerate the racket through the ball with the arm and wrist, and just skim the ball. When you can get huge amounts of spin this way, and can control it, then try it on a table.

Many players, when learning to loop or when under pressure, try to guide the shot consciously. This is a mistake and leads to a weak and erratic loop. Instead, let the shot go, accelerating smoothly through the shot. Don't try to "muscle" it - that just leads to spastic shots and a loss of control. Watch how the top players do it almost effortlessly, and with enough practice, you'll be able to do it. When you miss, adjust the shot on your next shot, and again let it go. If you still have trouble, there are two simple remedies: get a coach or copy the top players. And table tennis is a sport where you can absorb by watching - when you do so, your subconscious picks up on it, and can do a surprisingly good job of copying what it sees. One huge key - once you start looping competently, remember the feel of the shot - the entire stroke, from start through contact - and then just repeat. It's as simple as that!!!