Rhythmic tips and tricks
01 There are several tried and tested ways of smoothly segueing into a time signature or tempo change, rather than just instantly switching to it, which can be jarring. One of them is to end the bar before the change with a fill (most likely on drums, but any attentiondrawing instrument should be up to the job) that heavily features triplets. The reason this can make for an effective transition is that the triplets work as a disruptive, ear-catching intermediate stage of rhythmic oddness leading into the more obvious rhythmic structure that follows.
02 Another good way to lead into a tempo change is to again put a fill at the end of the phrase preceding the switch (not necessarily featuring triplets, unless you want it to, of course) and make the tempo change at the start of that bar, rather than the one at the start of the new section. This could potentially work with a time signature change as well, if your fill is designed cunningly enough to feel like a transition from one to the other. Or, if you’re switching to a ‘longer’ time signature (from 4/4 to 5/4, say), try putting a fill at the end of the transitional bar that just makes up the extra time (one beat in our 4/4-to-5/4 example).