I too had the same habit. Now what i do is first identify the error in the underlined portion (this step is very imporatant). Directly jumping to choices without any idea of what u are looking for leads to wastage of time and mind gets tired to reading all choices.
Starategy that i use:
1) Read the sentence thoroughly while understanding what it wants to say.
2) Identify error in the underlined portion.
3)If error is identified in step 2, go and directly eliminate choices containing that error. By now u will most probably reduce your options to two choices. Now maybe u can plug and see which makes more sense.
4) If error is not identifed in step 2, then do a "vertical scan" of all the choices seeing the "difference" in them. This differences in choices will possibly tell you where error lies.
All said, i feel what one really needs to ace SC is the ability to identify "error patterns" that are asked at GMAT.
i hope this helps.... keep doing practise and u WILL improve..!!