There's a video that explains the proper way to mount a bike (you can just Google it to find it). You should stand over the bike with one of the pedals 1/4 of the way from the top and as you push down on the pedal, you lift up and onto the saddle. You should dismount the same way.

I am CONSTANTLY removing my seat (because it's a quick release and I live in a large city and theft is very common) and even using paint markers and nail polish, I can never get a mark to stay on the post. What I do is take my bike to the street next to the curb. With the pedal in the down position, I get on the bike (which is lower because it's in the street and I am elevated on the curb) and with my left leg in the down position while sitting on the saddle, I get a slight bend of the knee (with the ball of my foot on the pedal in the bottom most position) of around 5%. Basically, you should put it as high as you can without having to rock your hips which will cause a lot of pain.

Chris