If you see the enemy team pick Teemo, Gangplank, Galio, or Jarvin, pick Singed at your own risk!
Don't change them, I beg you, they are too perfect. Ghost is for getting away from early ganks, or chasing down first blood, its just so sexy on him. Your first teleport should be used for yourself, after that tele to bottom lane's bush ward to gank, be sure you have your ulti+catalyst so you can turret dive for a few seconds.
This is a very balanced Singed build, It gives you everything he needs for early and late game domination. The only points that were floaters for me were Indomitable, I chose these to be a bit more ballsy in the lane phase (attacking enemy hiding behind his minions) but if you dont like these you can move them wherever you think would be better.
I know that most guides get fling first, and this is what you would normally do if you are expecting an enemy gank on your jungle, or if your team is ganking the enemy jungle. If you dont expect any ganks then pick up Poison Trail and go to your lane. The way you get first blood off with singed is simple, poison the enemy who is trying to last hit along with his minions clearing off that wave as fast as you can and getting him as low as you can with poison+auto attacks, as soon as that first wave is cleared you will level up giving you fling, pop ghost to chase him down (he should be half health by now) and fling him into your minions giving you Poison+Minion+Auto Attack for the kill.
Pretty self explanitory, Singed needs movement and magic damage. The armor is because Singed should ALWAYS be played solo top and 9 times out of 10 you are vs. an AD bruiser.
Ok the first item is a little situational. As I stated above, Singed should be played solo top. With that being said you will usually be facing an AD Bruiser in your lane. The Dorian's Shield will give you the most sustain possible with 475G. If your opponent is NOT AD, then you wont really need the armor as much so you should go with Saphire Crystal + Health Pots. If your opponent is NOT AD, and you have a gut feeling you can get first blood on them anyway with a little boost of Ability Power, you are welcome to grab a Dorian's RING and try to get that kill. Also I think Dorian's ring would be best if your jungle has already told you that he will level 2 gank your lane and its not a heavy AD opponent.
If you have Dorians Shield you should play aggressively, push his turret unless your jungler asks you not to, using poison trail and as his minions are down to their last tic of life fling the enemy champ into your minions for extra damage. This will get his health low enough to ping you for ganks making his jungle come to your lane instead of your squishy bottom lane. YOU WANT THAT TO HAPPEN! The beauty of Singed is he's extremely good at getting out of sticky situations. Once you practice enough, you can easily tell when a gank is iminent by the way your opponent starts to change his gameplay. The reason you want to be ganked, is because 1: you should be able to survive it 2: it keeps the jungler from ganking your mid and bottom lane carries 3: once you get good enough you can bait the jungler or the top laner within fling range of your turret. When you suspect a gank get ready to activate poison trail and ghost towards your turret (activate ultimate as well if you are 6+), when you get within range, fling the nearest one to your turret and put glue under him, poison trail through him and watch him die (hopefully). If you do not have ghost then don't be stupid, play cautiously by hanging out in a bush. When they run to your bush drop glue in the bush, fling the one thats trying to cut you off (the one between you and your turret) into the glue and run towards your turret praying you survive, also be sure to activate poison trail just as you fling him to the glue.
After getting Rod of Ages, your a friggin Juggernaut. There are tons of videos for late game singed you can watch on youtube. Basically you want to bait people into your team by playing extremely stupid until your about half health making them think they can kill you then ulti+ghost towards your team as they chase you, if they decide your poison trail doesn't taste very good and start to retreat, turn around and fling them + glue + run circles around them laughing as hard as you can in your most evil voice possible. During team fights, you want to fling the enemy carries out of position where they are open to your team to destroy them. Activate poison trail, drop glue and try to get your poison on all of the enemy team, and fling the carries, easy enough right? I cannot explain how easy it is to get your ELO up with singed. Nobody ever bans him and he's still a boss.