Unorthodox screenplay binding gets you off on the wrong foot. If your script looks much different from all the scripts coming in from the studios and agencies, then people feel you're an amateur and ... yes, give it to minions.
Screenplays should be on 3-hole 20 lb. plain white paper, bound with two 1 1/4" brass brads (ideally Acco #5 Brass Fasteners), with brass washers in back, and card stock covers. You should be able to get brads (aka "brass fasteners") at larger office supply stores such as Office Depot, or from Amazon. You can also get brass washers from them.
Why two brads and not three? Because you only need two to bind a script, one each in the top and bottom holes, and when you're making thousands of script copies a week, as the studios and agencies do, the cost and time of putting in an unnecessary middle brad adds up.
Don't use 3" brads (too long) or those skimpy #7 brads (they don't hold the script together). A few people use aluminum screw brads ("Chicago screws"), but it's not normal, and they tend to be slightly too long for 120 pages. Please never use those funny folding metal strips with sliders to bind the script. Personally, I like to take the bottom brad out when reading so I can flop the pages over. That's impossible with metal strips. Don't spiral-bind your script either. If we like your script we're going to run it through a copy machine so multiple people can read it. Ever tried to re-bind a spiral-bound script by hand?
Flatten the points of the brads back against the back of the script so they won't catch on people's clothes. Bashing the brads with a hammer will accomplish this nicely if you have brass washers; otherwise, fold each brad point backwards on itself, and then flatten them with a hammer.
Covers should be card stock, i.e. 80 lb paper. Any copy shop should have card stock. They can probably punch the top and bottom holes in them for you, too. Don't use clear plastic covers. For extra credit, use pre-creased 9 1/2 x 11" covers that fold over and cover the points of the brads. My printer (L.A. Print & Copy, (310) 445 3200), made fold-over covers for me out of my chosen card stock. Maybe they'd make some for you?
If you live on another continent, try to get 8 1/2 x 11" paper. Scripts on A4 paper look a little odd. But if you can't conveniently get standard American paper, don't stress about it.
Don't photocopy your title onto your cover.
Some caring people (including the William Morris Agency) were copying scripts onto both sides of each page to save trees, postage and schlepping, but they stopped doing it. People found double-sided scripts hard to read, and assistants hated copying them (and you really don't want to piss off people's assistants, so I can't recommend it...