This is a guide I use for Singed. I enjoy a tanky singed. one that has almost 6000 health at the end of the game. This is not an offensive guide. Its more for going in, initiating and doing some good damage so that your team can get the kills. Think of him as only assisting.

I like to mid singed. the reason is so that I can get my farm on. singed is an amazing farmer. his poison trail will allow you to eliminate minion waves in a matter of seconds. and in late game its really good to farm when possible, because this build is expensive. but with his farming capabilities, it makes it easier. Make minions fallow you all the time.
Also, if I dont go mid, i like to take solo top if there is a Jungler in my team, or I go with my carry. When I lane with my carry I assure he get all the kills so that he is fed and it will end up benefiting the team. Use the poison, fling and mega adhesive to get into range, slow and damage your opponent to facilitate the kill for your carry.

There are numerous masteries and runes that you may use to help you out. But I think of it as self preference. Some times I go tanky, some times I go AP. for runes its the same. you can get creative. Maybe you need more mana or maybe you need more health .. I dont have a set rune page.. call me a noob, but its just how I roll.

The way I like to go with singed it to max out my Poison as soon as possible so that I can destroy that minion wave as soon as possible. After that I max Fling and then Mega Adhesive. Depending on your oponents you pick Mega adhesive before or after you get your Ult. if you have a Tryndamere in your lane then pick it first, couse eventually he will come at you and you can fling, mega, poison.

I use teleport and ghost. Teleport is usefullt to get to places quicker. like if we are all mid pushing and there is a huge minion wave bot or top and its going to destroy the turret I teleport there immedietly couse Im the one that has the most farming capabilities. then I rush back to help mid.
As for Ghost, I use it to catch up to enemy champs or to escape. when you activate your ult, plus ghost and boots of swiftness... your pretty damn fast .. plus you can run through minions PLUS theres a trail of deadly *** poison behin you.

by the time you have RoA and Warmogs you will be very tanky. so dont over think turret diving to fling an enemy back so that your team kills him. or rushing a turret to kill a weak turret hugger . I use singed as the teams tank and Initiator. try to take all the damage from the turrets and help defend your team. Like fling oponents that are trying to catch up to a weak teammate or use adhesive to slow enemies that are following you when you are outnumbered.

Singed is a very useful tank. He can do loads of damage and you can definitely play around with your build. Make him a tank or make him an AP. Either way Singed is very fun to use and to dominate. He is banned a lot in Ranked, but when he is forgotten you will have a lot of fun. He is very diverse when it comes to the lane that he will take. Always stick with your team and make sure they chase you till they DIE!