Seems like a no-brainer, right? You just get some string, tie it to the corners, and put it up. Well the devil is in the details. Wind exerts surprising force on the banner, which is much like a sail. That force can rip out the grommets, stretch or break the string, and make your proud banner sag and wrinkle, if not destroy it altogether.
Fortunately we can learn from those who do it all the time. Here are three You Tube videos that give you the basics. I suggest that you watch them now, and then read my notes that follow. [As with any video you may scan the content quickly using the slider that appears when your cursor is near the bottom of the screen.]
Hanging with steel posts …
With rope …
I agree with the techniques described above but you can improve on them if you tie a loop in your rope about a foot from each corner of the banner. Instead of tightening the tie-ties, leave them loose so the banner hangs like a shower curtain. Then attach a bungee from loop to hanger at each end to tension the banner. Note also that white tie-ties are best for indoor use since exposure UV light makes them brittle. Black or grey ones are better for use outdoors.
With a wooden frame …
You can also make a pipe frame using large diameter PVC pipe and fittings. A ball bungee between pipe and grommet will tension the sign.
Be careful about where and how you hang stuff if the public may pass under or nearby. Although the fabric and rope may seem benign, the wind can forcefully propel whatever is attached to it. You don’t want your banner blowing around with flailing ropes and whipping hardware that lash out at passers by.