1. Don't jump directly to medium and difficult problems.
2. Don't try to solve every question. It will take forever.
3. Never look at the editorial before even trying and don't compare yourself with others.

Now how to best utilize this site
Sort the problems section easy to difficult. Now, further if you want to improve it, select the top 100 liked questions or the other option.
Try one topic at a time. It helps in understanding the concepts better.

Don't get disheartened if your solution isn't the optimal one. Even if it's brute force its a great progress. When I started I couldn't even do any of the easy question. Now, I'm able to solve 50% of the contest questions while getting end up with TLE or brute force approach on the rest.

The comments section was what I found out to be the best instructor. I sort the comments with most voted because nothing annoys more than watching hey my solution beats 90% of the submissions. Why it annoys me is because there's zero explaination, bad variable naming and trying to write one long line lengthy code. While after sorting, the explaination provided are so good that I learn like 5-6 problems and approaches going through one problem comments.