Hi, To plan and achieve merit in your 10th class the following are the tips you should follow:
1. You cannot skip any subject so you will have to prepare accordingly.
2. Make a study routine and plan in a  way that you cover all topics smartly.
3. Check mock and previous year papers, the marking scheme, how the paper is formatted and generally what chapter has how much weight age
4. You can track your performance through mocks as well.
5. Create goals for yourself, target it and try to achieve it.
6. Ignore/avoid any sort of diversions and just keep a eye on your goal.
7. Discuss from your seniors how much percentage you need to score to get your desired stream.

These points if followed systematically will help you alot.

Hope this helps.
All the best!