Do you need a lawyer to write up a will?

They have will kits that you can buy online or in certain magazines. Ultimately you need a witness, but to make sure there are no problems when you die, you should probably get a lawyer just to be on the safe side.

yes definitely

Not necessarily, but that might vary depending what country you are in. In the UK you can buy a form from the post office for about 99p which you fill in, get witnessed and will be considered legally valid as long as it makes sense. There is also infor on the Plain English website I think that outlines sample wills for straightforwards situations. If there is anything remotely unusual about your will, then get some advice or it could be comicated for your descendants