Not a parent yet, but hope I can be helpful.
I think most of what has been said in here is correct, but I would also say that, luckily or unfortunately, you can't be a different parent than the very person you are. I mean don't try so hard to be a certain type of person, because you will fail if that's not truly yourself. You might be 33 % gentle, 33% authoritarian, 33& of whatsoever you are suggested to be, but you won't be able to fake it for too long.
The kids will somehow "smell it" if you know what I mean. What type of parent you be depends almost entirely on what type of parent you had. Wait before drawing any conclusion though: what I mean is that if you had a bad example (which happens more often than thought) you will treasure your experience and learn not to do and learn a lot from that.
Same if you had a good balanced example at home: it will come out natural for you how to deal with your kids.
Be firm in your principles and provide him with a set of principles in which YOU have to show you believe. Doesnt matter if he aint gonna believe in those same principles or attitudes, but he will see what a man should be like.
Nonetheless, don't be afraid of showing your weak side, at time, it will make him intelligent, understanding and sensitive.
In the end, be yourself and if you're a good and balanced person you will have no big problem. My 2 cents.