Depending on the size of your dog, place him on a surface such as a table or get down on the ground next to him to best access his wound area. This method works best when your dog has long hair that should be shaved down to prevent contamination.
Gently cover the wound with a water-based lubricant to protect it from hair and other debris while shaving.
Use electric clippers to carefully shave the fur around the wound - start closest to the wound, moving outward, and cut with the clippers facing away from the wound. Use caution to avoid getting too close to the laceration and to prevent razor burn, which can further irritate the area.
Use a dry cloth to wipe away any loose hairs after clipping, then the lubricant from on top of the wound. Wipe carefully and gently.
Clean the wound gently with a warm, damp cloth until all visible debris has been cleared. Consider using an antiseptic soap such as chlorhexidine (2% is less irritating to skin than other common concentrations) to further clean the wound of bacteria - be sure to fully rinse any soap from the wound when finished, and to gently pat it (don't rub!) dry.
Dogs tend to lick at healing wounds as this provides them with a comforting feeling, and wounds can itch as they scab over and heal. However, this licking can delay healthy healing and can cause infection, so if your dog can't leave his clean wound alone, consider using a cone (Elizabethan collar) for 10-14 days to keep his tongue away from the wound while it heals. Also watch to make sure that he is not able to scratch at the wound, which can reopen healed or scabbed-over skin and further delay healing.
If you have chosen not to take your dog to the vet, monitor his wound closely for any signs of infection (redness, swelling, pus, heat, etc.) or delayed healing (of more than a week), in which case medical intervention is strongly recommended.