The key to training your dog to eliminate outside is to prevent accidents inside and to reward success. Adult dogs have better bladder and bowel control, and can "hold it" for a longer period of time than puppies. The rule of thumb with puppies is to take their age in months, add one, and that's the number of hours the puppy can "hold it" during the day..(i.e. A 4 month old puppy can be expected to be clean for up to 5 hours during the day).
Feed your dog on a schedule (he'll eliminate on a schedule, too)
Keep his diet simple and consistent (avoid table scraps and canned foods)
Choose an area, about ten square feet, outside, where you wish your dog to potty
Take dog on leash to the area, pace back and forth (movement promotes movement)
Do this for maximum 3 minutes:
if he eliminates, huge praise and play.
if he doesn't eliminate, keep him on leash, go back indoors, keep dog on leash with you or confined in a crate.
Try again in an hour; eventually your dog will eliminate appropriately and
You can give huge praise and play.
After each success, allow 15 minutes of freedom in house, before placing dog back on lead or back into crate.
After each 3 consecutive days of success, increase freedom by 15 minutes.
If there is an accident; decrease freedom by 15 minutes for 3 days.
REMEMBER DO NOT PUNISH ACCIDENTS!
IGNORE THEM AND REWARD SUCCESS!