Looking at other peoples levels is a good idea, but not the only one. You have to understand exactly why thos elevels were rated highly. My best suggestion to you would be to read the reviews given to your levels and improve them accordingly. Also take into account that some of the level designers you mentioned have been making levels for YEARS now. They could have been doing this for 5 years now, which is a LONG time to practice in making levels.

Also, I'm moving this to JCS, since this is JCS related, all the JCS questions asked there get answered even if people might thing it's a little inactive.