I would suggest you obtain the services of a buyer agent to help you. Your agent can guide you through the transaction and protect your interests. If the land is listed by a realtor there is no extra cost to you to have your own agent.
If it is not a lot in a subdivision, I would highly suggest that you ask for a survey. The seller can pay for that (it's negotiable who pays for a survey). Also if it is a parcel of land in the country, make sure you get a perk test to determine what kind of septic system will be necessary. There are also other factors to keep in mind, so a buyer agent is almost a necessity if you don't have experience with this sort of thing.
To find a good buyer agent, go to http://www.crs.com and find someone in your area with both the CRS and ABR designations. This will assure that you will find an agent with experience and who specializes in helping buyers.