So I play mainly Heimer and while I feel dirty answering I am down to help out (just please don't gank the Heimer if it's me plz :P).
Ganking Heimer is an interesting proposition because it is the hardest and easiest thing to do at the same time. The problem is that he is often (almost always if you're me, thank you wards) over extended so he is enticing to gank. However, he takes a different style and more coordination to gank or you end up feeding.
There are a few things that you have to watch for. First minions matter more to your gank than most ganks. If the minion wave hits my turrets and kills one, you come i and smite another one, and then you both jump on me, I'm in trouble. It isn't often that I'll let minions kill a turret though w/out replacing it before you could get to me unless you're already on or across my ward(s) though so that won't happen often. More likely what you're looking for is for minions to trigger the lasers from my turrets and draw their aggro. Lasers pretty much always target champs if they can and they HURT. If you come in from behind and all my turrets have lasers up my lane opponent probably can't join you for the fight w/out dying. If they try I'll stun them w/ grenade and ult rockets them for the burst kill 9 times out of 10 and then 1v1 you w/ my turrets and minions and summoner spells. YOU HAVE TO LET MINIONS TAKE AGGRO FROM TURRETS BEFORE GANK SO THAT BOTH LANER AND JUNGLE CAN JUMP ON HEIMER AT THE SAME TIME.
Second, never gank heimer w/out your smite up. If you have one that hits me you need it for the extra burst so you can kill me and get out. If you don't have one for hitting champs you want it for one of my turrets. This leads to section 2 b. Heimer ganks need set up. If your laner and me are trading and they are killing my turrets and I'm replacing them (obviously this doesn't apply if I have them so pressured they can never kill my turrets w/out losing the trade so hard it isn't worth it) you need to work w/ your laner to time the gank so they drop at least one of my turrets before you enter lane. This way you can smite down a second turret if you aren't smiting me and suddenly I have 2 instead of 3 even if I immediately replace the turret you smite w/ a kit I'm holding. That lowers the damage against you.
Finally you need to have a plan and play to your strengths. If you have a tanky laner w/ a burst jungle have the lane take aggro right as you go in to hit me and burst me down w/ them like it is a tower dive. If you have a poke mid then they should be poking me and you can block the incoming wave of minions so your minions are the only ones in my turrets and distract them so you can get in close to engage without taking massive damage before you get to me. There are other combinations but basically think about how to remove Heimer's protection so you can get to him, or how to mitigate it so you can survive. If you get onto the Heimer he is usually dead bc we are squishy.
P.S. often it is about blowing summoners and coming back. I often run two defensive summoners and have had a lot of double kills where the jungle and lane engaged at slightly different times and I dropped ult q and then stunned one or both and ran to one side only to flash back to the middle of my turrets and run to the other side and get a double as lane and jungle ran back across my turrets chasing me only to die as I exhaust or heal and they realize they don't have the damage they expected to be able to chase me down and kill me after all. The good jungles and lanes just run out of the turrets when I flash back in, and come back after healing up a bit and kill me when I can't drag out the fight in my turrets and kill them.