Building a Call of Cthulhu / Delta Green character.

[Silent Wayfarer]

So I'm going to be playing in a Delta Green campaign as an entomologist of sorts. I want to make a competent character, but I have next to no experience with the system.

Can someone tell me what are the pitfalls I should be looking out for? Critiques / reviews of the system (especially scathingly hilarious ones) are also appreciated.

Thanks in advance.