What do I mean by this? What is supporting a gank? Well my friends, supporting a gank is the actions the lane takes in order to assist their jungler in killing off their laning opponent(s). There are a myriad of complexities to this process based on situation and champions involved, but there are a few basic concepts that people seem to have a hard time understanding.
Here is a diagram of a lovely bot lane (pretend top tower is yours despite label):
Its pushed hard, the enemy has been crapping on Trist and Taric for the whole game, and you can bet they have been whining like little bitches for a gank. Now their dreams have been answered: friendly trundle has approached the bot lane completely undetected, and hes ready to gank! Now he is sitting in the bush waiting...."what on earth is this trundle waiting for?" wonder Trist and Taric. They conclude he must be a shitty jungler.
THE LESSON: When your lane is getting ganked, 99% of the time, you, the lane, need to make the first move. There is nothing more infuriating as a jungler than to show up in the above situation, and have Taric and Trist continue to sit there under the turret, so far back that they cannot assist with anything.
THE BEST WAY TO INITIATE A GANK IS WITH THE LANER(s), JUMPING INTO A BAD FIGHT.
Yes, thats right, you need to engage in a shitty fight that you will lose. Do something retarded, or at the very least dumb. If you are a top lane, just go up to the enemy and start hitting him. Trade damage in a way that the enemy KNOWS THEY WILL COME OUT ON TOP. This way, when the jungler leaps out of the bush, the enemy is already at probably half health and may have blown all of their skills. EASY KILLS.
Think of it this way: You are a Nasus going up against Renekton. You are winning the lane and he is pushed back under tower. You are in the middle of the lane.
Situation A: Trundle leaps out of the river bush and charges you.
Situation B: Renekton comes forward, hits a few CS and then starts attacking you.
What happens 90% of the time in these situations?
Result A: You immediately realize this is a 2v1, throw wither on trundle and run back to your tower. Fail gank.
Result B: You know you can take Renekton, so you attack back, trade some damage and then pop wither on Renekton to slow his DPS and allow you to get the kill. Suddenly Trundle appears mid-duel and pillars you, you are left with no chance to escape and die.
IF YOU CAN SURVIVE IT, ALWAYS TRY TO INITIATE A DAMAGE TRADE OR DUEL IF YOU HAVE A JUNGLER IN POSITION. THIS WILL RESULT IN OVER 9000% MORE SUCCESSFUL GANKS, ESPECIALLY IN SOLO QUEUE.