Lots of head movement to avoid his punches, cut off the ring and close in. Then work him on the inside. It's a bit of work to get in sometimes (jab ur way in, throw feints etc...) but once you're in the pocket - make it count. Hard shots to the body, try to wear him down & take his legs away. I'm sure other people have other ideas. There's more than one way to skin a cat, but that's what I would do.
The jab never worked all that well for me. I used it mostly as a distraction to close in for a hook or cross. Basically, just emulate Tyson or Marciano who both were fairly adept at overcoming their shorter reach.
Watch some tape on Dwight Quawi He fought out of a crouch using an up jab to play hell on his opponents. This all really depends on the type of fighter you are. You can fight smart and make your opponent give up onhis reach, most of your opponent will figure they can out jab you with their longer arms. You can train to jab on top of your opponents jab while stepping in, this will put you in position to work on the inside. You can also do as Tyson and hook over the jab if you have that type of power. The thing is to take away what your opponent would feel would be the best weapon against you and thw ould be the jab, then you would have to work 2 or 3 more options for the adjustment your opponents would make when you take their jab away. If you took my fighters Jab away I would have him give ground and jab your arms and gloves so that you would have to reach to get to him to get you off balance for counter and combos. Watch some talpe on some of the shorter champions and pay attention to the adjustment made during the entire fight, make sure you watch serveral different champion and try and use the things you like and are willing to work on get good at those and when you have your A and B plan go back and learn a couple of tactic you don't really like to keep yourself versitile.
You need skill, you need to have movement that makes you evasive like pernel whitaker or qawi or tyson that gives you an opening for you to work off. It depends, are you strong, can you judge distance well, can you block shots with ease, what are you best at?
Most short fighters who have trouble with tall fighters either are bad at cutting off the ring or are not trained to take 2-3 steps in before unloading. Everybody is taught how to step in with one punch or step in and then punch. But rarely do trainers teach fighters to take multiple steps jabbing in or slipping/bobbing your way in. Taller fighters usually have a reach advantage, but their longer lags also gives them a stride advantage. One step backwards for them can mean two steps in for a shorter fighter to cover the same distance. So practice multiple jabs and multiple slips while step-step-stepping forward at the same time. Make sure you're not leading with your head but are in fact stepping in with the bottom half of your body. The top half is attached to your waist, so it will naturally move forward with the bottom half. This way, you don't lose balance and can fire off either hand. To cut off a tall mover, simply move sideways with the opponent while maintaining punching position, cut his movement off and force him to change direction while carefully making him back up with feints or non-committal jabs. Once he changes direction, immediately slide the other way and force him to change direction again, all the while backing him up until his back is to the ropes. Then you can step in and unload because now he can't back off anymore. If he's real good at sliding laterally, you have to force him into a corner before stepping in with an attack.
If you don't lead with your head as a shorter man, you are wasting your time trying to get inside. Great short fighters lead with their head, bait in a jab, move their head and counter.
A couple of things: 1) Either be inside or WAY outside -- don't allow yourself to get in that middle distance where you are the end of his punches and you can't really reach him. 2) An effective technique for getting inside (one of many) is to block the opponent's jab (or even if it lands, actually) and follow it in -- it takes some practice and timing, and you have to guard against the right hand that may be behind it. When he throws a jab, his hand is going to go back to its stance position, and you are less vulnerable moving in if you time it so you step forward as his hand retreats back to him after he throws it.
