While in laneing faze singed is known for farming under tower so when you a little aggressive it can through people off. The basic idea is to turn you poison on only just before you fling them, to use your slow to keep them there and auto attack them when they get to close. NEVER chase though and NEVER use your slow to chase/ catch they will have to get close or they will loose there lane. When facing another melee champ its OK to push out to the third bush but I would stay more to the middle when against a ranged champ. Only using the slow first when there's a 100%-ish chance to kill

As for farming the tear you always want it on when your at the platform. In lane try to a bit more conservative though only using mana when your going to combo someone or turn on the poison real quick to last hit a minion. As for returning to lane i like to leave it on to im out of the base and don't turn it back on till i get to my lane. late game like when the tear gets around 500 stacks its ok to leave it on longer and longer and eventually you want to just leave it on.

Homeguard
While this build is is for being aggressive in lane after the laneing faze diving and chasing isn't ever a good idea anyway. Its better to wait for the right opportunity to single someone out. That's why I get homeguard it's instant recharge and if need be i can get to a different lane very quickly.
G.A.
If your doing your roll and taking all the damage I say why not. not to mention you'll be dealing tons of AP damage its not like you couldn't clean up after. You'll have about 243 just from items.