Hi,
As we are not a "sparring" art in the common sense, my answer is more geared to a "street" encounter, although it could probably work well in a sparring situation (with a bit of tweaking), I guess...
To enter and apply a technique (attack, strike, kick, grapple etc) on an opponent, a few things need to happen. You need to be able to breach distance in order to reach them, and you need to avoid their potential strikes/kicks/grapples etc. So to do that, there are a few tactics and strategies which can increase your chance of success.
Probably the most classic is the fake. But remember to have a plan of action here, don't just throw a variety of empty gestures, and hope a follow up will connect. In basic terms, throw a fake deliberately, and treat it as if it is real (because otherwise you risk your opponent "reading" that it isn't, and you won't get the reaction you need) And remember the effect you want your fake to have. Don't just use it to "get a reaction", use it to get a specific one. Fake high, and come in low. Fake low and come in high. Fake left, then come around from the right. As you throw a fake (say, high for instance), you bring the opponents attention to that area, as well as often their defences (their hands, in most cases). This then leaves the lower body open for your entering movement. But a fake won't always work, so stay aware, and be prepared to use multiple fakes in order to gain your opportunity (more sparring than street there...).
Fakes aren't just actions/strikes, though. Street predators (different from a street fighter, by the way) utilise a variety of "fake" tactics in order to get close enough to attack a victim. These include faking friendliness (Hey, man, how you goin'? You doin' good? Come here... *WALLOP*), being more of a "sleaze" (Hey, c'mere. Got somethin' t'show ya... *WALLOP*), being overly aggressive (in order to overwhelm a victim into freezing, relying on cultural conditioning to stop the victim hitting first, or even at all in most cases), or just asking an innocuous question ("Hey, man, you got the time?.. *WALLOP [as you look down to check your wrist]*).
Those are the way they are used by a street predator, and yes, there are more, but those are pretty common. However, the same tactics and ideas can be used by the "good guys" as well. Basically, you can be any of the above for different circumstances. Recently we held a class on what we refered to as "Transitioning Distances", covering both how to get in, and how to extract yourself if required. The "friendly" approach works well if you need to get in close to apply a restraint and removal-type grappling approach, for instance. In our Group Defence, we teach that striking first is the best option, and pre-emptive striking is covered quite regularly. One of our common methods is to use the inniocuous question to occupy the opponents mind, and then strike while they are thinking about what you are saying. And being overly aggressive (when teamed with a good understanding of distance) can help as verbal dissuasion, stopping someone from continuing.
As for handling the differences between the physical assets of different people (arm reach, for example), there are tactics of out-flanking and angling to apply here. Move either to a position where his targets are opened up (if they have their left foot forward [orthodox], move to the left), or to a position away from them (if they are orthodox, move to the right). This is a little hard to discuss, but you should be able to find a position where you can reach them, but they can't reach you. Play with it, and you'll find it.
Oh, and finally, Msby, the use of a kiai/kiap is a traditional form of occupying the opponents mind. In swordsmanship, you may flick the tip of your sword up towards their eyes for the same result. But there are certainly classical techniques that use exactly as you describe for much the same result. Nicely done.
