Don't listen to guy above.
Always run Spellbook swap on Singed. Early game, you got flash and teleport for obvious safety reasons. Lategame, when you run around like an unstoppable maniac, you change it to either ghost + flash, or ghost + ignite/exhaust depending on what your team needs.
Go righteous glory first for obvious reasons. Use his "puff" mechanic to double tap Q and save tons of mana. Rylai's is next almost always. Then Liandry's if you're against tanks, banner against AP champions, and ZZ'rot if not.
After first cannon wave, go behind enemy tower (obviously pay attention to where enemy jungler is) and proxy. You win lane for free. Don't lose too much health and mana before the first cannon wave. You'll get all the cs you lost back when you start proxying, and your enemy will either cs under tower and lose tower health constantly, which is basically drops of gold every few seconds for you, or he will chase you and lose tons of cs and experience in the process.
Takes practise, but he's still incredibly great, especially against melee matchups. Just never, ever pick him into Yorick. His W is a free kill on you every time it's up unless you flash.