The main points that will really help are -

The solution you get is alcohol based, and it will not hurt your phone. So when you have the sticker in your hand, not only absolutely soak it, but also spray the screen of the n900. That way, when you whack the sticker on, and its not perfect, you can simply slide it into place. (By soak, i mean it man, until the sticker is dripping!!)

When its in the right place, with a tissue, gently rub from the center to remove some of the bigger bubbles. When they reach the edge of the sticker, the excess solution is immediately absorbed by the tissue.

Then spray the top of the sticker. Not loads, but a good coverage. use the little card that comes with it to gently glide over the screen, removing any remaining bubbles. Then dry with the tissue again.

For edges, if you do the main part first, and let the edge bits dry a little (5 mins) before you press them down, they will stick much better. There are some good vids on the zagg website regarding corners and edges.

It will look pretty rough for about 2 days, little bubbles here and there, and a speckled effect. That will disappear totally, and the finish will be perfect!

It takes some time, and patience, but like I said, the most important thing is to go to town with the spray solution that comes with it, it means you can make mistakes, move the sticker into the right spot, unpeel it ect. without worrying about ruining the sticker.

Generally when I do a full body one for an iphone/psp/ds ect, i'll use just about 80% of the spray/solution. Always a good idea to leave the phone turned off for an hour or so after you have fitted the kit, just to ensure any excess amount of liquid has dryed

PHEW. Hope that helps in some way!!