i prefer 120gsm paper for easy folding... i used any normal stationary glue to glue stuff... but i must have a small paint brush to glue my work... ruler, i use metallic ruler to help me in folding, cutting mat (this is necessary), A Pen knife, Made in Japan Scissor (why? I dunno) but if you can find scissor that being used in hospital is even good!! cotton bud (help me to strengthen my gluing in some part my finger can't reach) and most of all a set of working brain (hahaha...just kidding)
Well we can all agree that a scissor is necessary. And a (color)-printer would be nice.
I print my prototype-models on 120g paper, but the end-result on 180g glossy photo paper.
When you start printing stuff on 180g paper, you need to scorn the paper before you can fold it (to get those nice straight folds). And then a scissor is not enough... I use a knife with a very small blade (it's available in any hobby/art shop), a metallic ruler and a cutting mat (can be hardboard or something bought in a shop).
For glue: we had an discussion about this which you can find here, and a comment of mine can be found here.
And for those hard-to-reach places I use a sate stick; for applying glue and press pieces together.
That's the stuff I use for building paper models...., but if you want to create models or design skins for other models you need software.
There is discussion about that to: Tools (Software), but the most important stuff you need is creativity!
I print on normal 80 grams paper, then glue it with Spray adhesive onto a 120 grams paper. I score it with a dull blade I have and then cut (With a good sharp pair of scissors) and fold it (Scoring before cutting helps). I use normal glue, but I'm buying a hot glue gun to see if it looks better. Also, I hope that I can glue glossy inkjet photopaper with it. (Normal glue just doesn't work)
I just started using matted photo paper, I don't know the weight, I think around 180g, but it's thicker than regular paper but not as thick as cardstock or business cards. They're really easy to fold, and it doesn't crack when you fold it (which was a problem I had on this other matted photo paper I used). Anyways, I've been using white Elmer's paper glue and I apply it using a paintbrush. I gotta have a good pair of scissors and my Exacto knife set. I also use tweezers to help glue parts together. These are regular tweezers for plucking eyebrows and stuff (I stole it from my wife). They're really good because they're like mini pliers that can hold and clamp things down w/ the flat surface area. It's very good for holding pieces of paper together and waiting for them to dry. I use old magazines as my cutting mat, and I score using this rounded metal keychain thing I got for free from budlight.
I use a Cannon Ink jet printer which I purchased specifically for printing templates. I've experimented with all sorts of paper stock, I think it's worth doing - certain paper suits some models better. I had this discussion with my girlfriend a while back, she reckoned that if the look I was trying to achieve with my paper toys was to emulate the look and feel of vinyl toys, then glossy paper was the way to go. I've used glossy for putting together Shin Tanaka's Spiky Baby models for example, and they look great.
I do find that the type of stock you choose dictates to a large degree the strength of glue you'll need for the job. I use Evo-Stick Wood adhesive for thinner, matte photo paper templates and super glue for the thicker, glossy ones. (Watch out you don't breathe in that vapor, it can be nasty!) Most of my models have been printed on Cannon Matte Photo Paper, 170g. That may be a little too thin for some, but it folds nicely and doesn't tear when scoring.
As for the other essential tools - sharp scissors (i use hairdressing scissors, sharp - but can blunt easily),
a self-healing cutting mat (OLFA is a good brand), a craft knife or scalpel - I find X-Acto blades to be the most hard-wearing. For scoring and folding I use a ballpoint pen (keep scribbling 'til it's empty of ink) and a non-slip steel ruler, this was a great purchase, the Helix I use has two rubber grips to prevent slippage and a groove to guard your fingers from your knife. Also get a pallet for glue and cocktail sticks for application (especially handy for intricate tabs), I have in the past used paper clips to hold those tabs that just don't want to bond, but now I use a pair of tweezers.
One last piece of advice... be patient with yourself, you will get better - like everything else, skill comes from practice.
Hmmm... people always ask me what kind of paper did I use to make my stuff, well that's depend on what kind of papercraft I'm making. If it's something like a bulky robot with a lot of parts, I will go for 100gsm or even more... but if its simple and take less than 1 hour to build, I will use any kind of paper that I can find... even a scrap paper with a blank side will do...
I keep both scissor and cutter at my side, I will use either of them depending on the template's shape or some time it's just depend on my mood... I use liquid pvc glue, normally I will drop 1 drip of it on a paper then, I will use toothpick or something to scoop the glue and paste it on the papercraft. By scooping the glue with something like toothpick, you will reduce the chance of excessing the glue and make your papercraft looks gluey on every joint...