Outdoor lights must handle rain, snow and cold. Look for products labeled for outdoor or wet locations and check the IP rating when one is listed: IP44 resists splashing, while IP65 and higher are better protected against rain and dust.
Bulb size changes the look. Large C9 bulbs give the classic roofline glow and are visible from the street. C7 bulbs are a little smaller, and mini lights work best wrapped around trees, railings and bushes. Measure your roofline or trees before you shop so you buy enough length, adding a few extra feet to reach the outlet.
Plug outdoor lights into a GFCI-protected outlet and use outdoor-rated extension cords. A plug-in timer or smart plug turns everything on at dusk without a trip outside. Test every strand indoors before you climb a ladder.
For faster setups, compare icicle and net lights or a light projector, and add pathway lights along the walk.