I really disagree with this. The reason you don't want a tight grip is because a tight grip increases tension in the hands and arms and tension absolutely kills speed. If you are tense, there is very little flow and "allowing" of the club and arms and hands to release.

Now, that's not to say that a tight grip cannot work for some people. Like a lot of things in golf, there are no absolutes. It is worth a try, but there is a very, very good reason why so many teachers advocate loose grips. I wouldn't expect this to fix a lot of the problems and may lead to other issues.

------------------------

Now that I've thought on it some more, to answer the OP, the best way is probably to take a lesson and pay for the professional guidance and advice. For almost everybody, it is the quickest way to the most significant improvement.