Depends what tyres and rims you have.
Assuming your tyres will work then my method is:
Cut a valve with a thread on it out out an old tyre, leave 2-3mm of thick rubber arround the stem.
Wrap the rim with electrical tape, building up 2 or three layers making sure it goes from one bead to the other. The exact amount of tape depends on the tyre and rim, i've just done some stans rims and they only needed one layer (on top of normal fiber rim tape to stop it bulging though the spoke holes), some DT rims needed about 4 layers, my mavics needed almost a roll each (still only about 20-30g)!
Put the valve in, and do the locknut up. It might need to be done up with pliers to get it tight enough to seal the rim.
Now try and inflate your tyre without a tube. If it wont go up at all make sure it's definitely over the valve so the air isn't just pouring out. If that still doesn't work add more electrical tape. It'll probably go flat in well under a minute, you just want to see if it works.
Once it goes up once, take a small section of and pour in some stans fluid before re-inflating. Give it a good shake, ride round the car park, etc, to get it sloshed round good and proper. It'll prossibly leak round the valve, if it does tighten the lockring up (gently with pliars might help) and shake fluid round that area.
Hpefuly it'll now work.