I have been reading some of the tips here but i never seem to find them well.I tried sliding my fingers on the notes and it started to show a little but i was wondering do you do anything special with the embouchure?

Go over to woodwind.org and do a search- they have heaps of information on glissandos.
You should drop your jaw so that the pitch drops, and slide up to the last note. To practice making the pitch drop, play with just your mouthpiece until you can make the pitch drop an octave. Then practice dropping pitch on all the notes of the chromatic scale. Then apply all this to the glissando. There are changes inside your mouth, but the people at woodwind.org explain them a lot better than I do. I am just learning to glissando at the moment.

Do you find it really hard, Rachel? I can do it sometimes but my boyfriend is great at it. He`s tried explaining how he does it (he changes the shape of his throat - opens it up, I think) but it won`t work for me. He doesn`t even use his fingers at all. I can`t do it without using at least a fraction of my fingers and it ends up being uneven and jerky, no matter what.

I mean, a gliss upwards, not down. I can gliss downwards way over an octave but can`t gliss up.

I have heaps of trouble with it. I find it easier to gliss up than down. It sounds really jerky, but it is improving.

I`ve been messing around with the glissando myself, to try to play Rhapsody in Blue. The basics go as follows:
If you`re really good with your mouth, you can do it without much finger work. I`ve heard people claim that they can drop the pitch a ton, and finger up chromatically without the individual notes coming out. Then, once your fingers are at the note you want to go to, you bend the pitch up.
Or, you can do it mostly with your fingers. The technique called half-holing is when you slide your fingers off to the side very slowly. Start with the lowest finger, then when it`s about half off or a third off, start sliding the second finger off, and etc.
Personally, I wasn`t very good at either of these. I can`t bend the note enough, and when i try fingering it, the "inbetween notes" don`t come out. So, I tried both at the same time, and it worked wonderfully.
First, you put your tongue in the back of your mouth. This drops the pitch a bit, and i`ve noticed that the sound becomes harsher, or dirtier. If you half-hole with your mouth like that, the "inbetween notes" come out much easier, and I am currently able to do a very smooth gliss from a high G up to a high C. Much luck, and keep practicing