B.Sc

1)The first and the foremost, you need to fill an online application for Delhi University mentioning all the courses that you wish to seek admission in. Though you can also go for offline application, but it will be convenient to fill it online. You will also be required to fill your class 12 board marks subject wise.
2)Next, wait for the cut-off lists.
3)For the B.Sc courses, the cutoffs are to be calculated as
For Physics, Chemistry, Zoology, Botany, etc your cutoffs are calculated as per your percentage in PCM
For Mathematical Sciences, Computer Science, Mathematics and Statistics, cutoffs are calculated as the aggregate of marks in mathematics, one language subject and two best elective subjects.
For B.Sc pass courses, again your aggregate of your marks in PCM will determine cutoffs.
There are yet another courses, which follow different procedures. To know about them, you can visit the official website of DU
4)DU releases it's cutoff list. It will be available on the DU's website and on the associated colleges' websites. Also in some of leading newspapers. Look up for your course. Check, in which college's cutoff you fall. If you wish to take admission, make your move.
5)Rush up to the college. Get your documents checked. Do not forget your DU application. And make sure that the course in which you are seeking admission is mentioned in your application. Fill in the required forms, attach necessary documents, deposit your fees and Bingo. You made it to DU.
6)If by chance, you could not make it to the college of your choice in first list. You can wait for the subsequent lists. And follow the steps 4 and 5.
For better knowledge, check the official DU website. Check it regularly for more updates. Also download the this year's admission prospectus (once available) to understand DU more clearly. If you are near Delhi, you can also visit the Open Days Session of DU for better knowledge on admission process. The details of these will also be available on DU's official website.