How to trademark a logo?

I have done this in the past for several comapnies. It's fairly complicated. You need a solicitor to do it for you and it's about 500-600 Pounds. At least it was in the late 90s. Point is though that a logo is protected once you start using it. You only need to be able to prove that you used it first. Apart from that it will only give you very limited protection.