Do some Internet research on the company that wants to option your screenplay. Find out if they're a large or small company, how many projects they've made, what the budget of those films were and how much the screenwriters were paid. You may need to subscribe to a screenwriting database like Done Deal Pro to find the actual figures on what was paid. Or you can sign up for a one-week trial subscription to access the information.
Figure out how much you hope to make on the script when it sells (realistically) and then figure two to 10 percent of that for the option. Remember that options are done most often for lower-selling scripts, so you want to be prepared for a lower offer and not be too quick to turn it down.
Go to the meeting and listen to the offer. Read over the option agreement and ask about the purchase price, length of option, credits upon sell and rewrites. The longer the option, the more they should pay you. Most options are for three months to one year, with the most common being set at six months. If they offer rewrite options in the contract, then discuss what those will pay and how to put it in writing. Make demands and/or requests as you see fit. Feel the energy of the room to see how far you can push it without losing the contract but still getting what you want.
Take the contract to a legal adviser, lawyer, entertainment attorney or agent and have her look it over to make sure everything looks right. When everything has been settled and the red flags adverted or changed, sign it and make a copy. Then mail or deliver the contract back to the production company.
Wait to receive your option check. Make a xerox copy before depositing the check to keep for your records.