Secret: Time is NEVER on your side when you are buying. Never forget that. Keep in mind that if you are looking to explore the viability of a purchase, a good starting point is the LOI. Once you get beyond the "overview" of what you and the seller are looking for, detail everything out in the purchase contract, and keep all of the above in mind when doing so.
L. A simple but sometimes overlooked item. Include language that allows the LOI to be signed in counter_parts. Again, this is a small item but it can save you days in the process. A Letter of Intent is a terrific tool for helping to get your transaction off to good start and moving it toward closing more efficiently. While the information above certainly isn't exhaustive, it provides a great platform. As stated above, always consult the proper professional before acting.