See, Data Science is a field in which you will have to deal a lot with Mathematics and Computers. Your day to day job will require you to do data extraction, clean data, modify data, model the data, and finally present some useful insights on data. So, having a strong fundamental in computers and in general programming languages is a must. Following are the things I would recommend you to learn before joining a B.Tech in Data Science:

1. Learn the basics of computers

2. Learn Python in depth

3. Learn searching for datasets

4. Learn MS Word, Excel and Powerpoint

If you have these skills before joining the programme, the rest of you journey will be a breeze. Hope I have answered your question. All the best!