Here are some things apart from working on your engineering concepts, that you should do for a complete preparation for GATE:

1. Solve previous years GATE papers: Solving previous years papers gives you a fair idea of what the actual paper would be like. It also brushes up your basics and exposes your areas of improvement.

2.  Solve as many test papers as possible. This actually is the best way to keep improving as you prepare for GATE.

3. Analyze : Analyzing your test results is a very important part of taking the test. If you do not analyze, the test does not add value. You should minutely analyze and define as to where you could have scored more; analyze your accuracy rates in various topics and maintain a topic wise datasheet which lists your performance topic wise for different test papers.

4. Simulate actual test environment : This is very important. The actual test happens in a classroom, and is timed. When you take up the test, switch off your cell phone, have a timer which times your tests, and avoid taking any breaks. Also, if possible, take up a mock test series which enables you to take the test in a classroom environment.