i have a wooden vivarium and was wondering if i use a heat mat what do i use to cover it so it wont burn my gecko but will allow the heat through (using newspaper substrate) if i shouldn't do that should i use a heat bulb dimensions of viv 3 foot wide x 1 foot deep x 18 inch high

generally heat mats are fine to use they wont burn the under belly of a reptile as they use infra red beams to heat the furniture of the vivarium and only give off a low heat, i use mine as part of a night time heating set up for my iguana its on the wall and he just sleeps up against it but i do leave it on 24 hrs as i have a large vivarium to keep warm...
a 100w heat lamp will give off sufficient heat in a tank the size you have described and give a good gradient so its hot in one end and cooler in the other.

An under the tank heater or a heat lamp with either a night light or a ceramic light bulb in it. You can still put the heat mat under the wood tank. and you really need to get a different substrate. Either sand or Eco Earth.

you can buy proper floor covering for lizard. from good pet store.a leopard gecko only needs a heat mat. you can put a bulb for you to see him.they also like to hide so you need a house as well