Remember that the sheets pull in and let out the sails. Pulling the mainsheet brings the mainsail closer to the centerline of the boat. Pulling the jibsheet brings the jib closer to the centerline.
Once the boat starts moving forward, position the tiller so that the boat is not turning to either side. If the sails are loose and flapping, pull in the mainsheet just until the mainsail stops flapping and takes shape – you will feel the boat speed up. Then pull in the jib sheet until the jib also stops flapping.
There is one simple general principle for where to position your sails. The closer you sail toward the wind (close hauled), the more you pull in the sails. The farther you sail off the wind (broad reach), the more you let out the sails.
The photo at left shows the sails far out to the side as the boat sails downwind. (The wind here is blowing from right to left.) The photo at right shows the sails brought in close as the boat sails upwind. Notice the boat heels over more the closer it sails into the wind.