You should never try to negotiate a term sheet by yourself. You are responsible for the main business points, and it's going to be primarily a negotiation between you and the investors, but an experienced lawyer is a necessity. A lot of times, a sophisticated investor will make you get one, even if you don't want to. The lawyer should be able to tell you what the terms mean, how they affect the overall deal, and whether the term sheet includes unusual terms or terms that don't make sense.

If all goes well, the terms will become a set of formal legal documents, easily more than 100 pages all together. Getting a lawyer on board when you negotiate the term sheet will mean that he or she is familiar with the basic deal provisions and doesn't have to ramp up to work on the full documents (saving you time and money).

Try to pick a lawyer that has experience with financing startups in your sector, and understands your business. Having a lawyer friend "look over the documents" for you isn't going to cut it. A good startup attorney will talk with you-for free, and before you actually hire him or her-about your business, your goals, and your financing needs.