Optimally you will avoid fights, but you will eventually end up in one. Use a combination of stealth and melee weapons. Hide and wait for an enemy to pass. When the icon becomes yellow, take them out with stealth or sneak up on them before killing them. If you are not outnumbered, consider luring them into better areas for a kill. Run around to make some noise to bring them to your position. Hide in the shadows then use stealth to kill them.