Hi,

If you have a good chance of getting a particular college you can fill / select that colleges in the first preference to secure a seat.

Generally in admission counselling  the colleges are alloted according to the preference given by the candidate.

So if according to your rank you have chances of getting admission in a some college than if you keep them in higher preference your chances of getting a seat get increased.

If you select thee colleges in which you have less chances probability is there for you to get the difficulty in securing a seat in those colleges.

Hope it helps.