It says that you have to have be renegade for over 75% of the time. For example, I just did a quest, where I ended up getting 25% renegade and 8% paragon. I've also run into a few situations where I got a few paragon points. Will this affect me getting my achievement? I'm currently on Noveria, second planet.

No, you should be fine. I believe you can get the renegade achievement if you just do a few of the main things that get you the 26 point actions.

yeah getting both side points isn't a bad thing. just be a d-bag thruout the game and you'll hit renegade, but a major boost to getting renegade earlier in the game is double-crossing. lie whenever you can, and noveria has at least three major opportunites for it.

this game is different from other morality games in that you can theoretically have full renegade and paragon meters at the same time.
So paragon points dont count against renegade points

I was able to get both Paragon and Renegade achievements on my second play through, actually getting them both up to 100%, so yes, it is possible.  It's not really being either one 75% of the time, it's filling the corresponding meter up to 75%.

It should there still isn't a patch out yet. Just check Xbox360Achievements.org for the guide I was able to do it during my Insanity run.

Noveria is one of the best places to get lots of Renagade points as there is an oppurtunity to a bad thing near the star of that planet. You should be fine getting the achievement as you aren't too far into the game, just act like a real jerk from here on out and you'll be fine.

to get the achievements, i just go full paragon on the 1st playthru and then full renegade on the 2nd.