The first thing to do is to determine where exactly you want to hang your outdoor light stringers. You will want a secure anchoring point at each end. These anchors could be trees, posts, the eaves of a house or porch or some other surface that offers solid support.
Next you will want to measure the distance between the supports so you will know how long your string lights will need to be. Make sure to order string lights with a linear footage a bit longer than what you have measured. Many string lights can be connected end to end, so keep this in mind when figuring the length of the string lights you need. Make sure that the ones you order will meet your length requirements.
When you are ready to hang up your string lights, connect a screw eye to each support. Then it is simply a matter of connecting your string lights to each end with zip ties or other connectors. For added support, you can connect your string lights at intermediate points, like house eaves, with zip ties and more screw eyes or with the loops that are included atop many light bulb sockets.
For longer light strings, it is a smart idea to use a hanging guide wire to provide extra support. This will help keep your light stringers from sagging and drooping and will give your job a professional look-and may help prevent taller friends or family members from walking into your lights. Simply hook the guide wire to the screw eyes with the wire's screw clamps and connect the lights and wire with zip ties.