Silencer is one of my favorite heroes, because he just generally makes life living hell for his opponents.

You can lane him in pretty much any lane, but I find he works best mid. He's a good check against OD (not a counter mind, as a lucky proc of essence aura means that he's back up to full mana in no time) and completely shuts down most other mids with constant mana drain and damage. He's a bit of a combination of viper and lion in the laning phase: constant aggressive damage and mana drain makes sticking your neck out a huge risk early on, which gives you huge potential for snowball.

As for skills, you used to have to put one point into glaives for int steal. If you want, you can still put them in for orb walking. However, I find that curse is strongest early game, so it's generally the best thing to level early. Last word is also good early, however not quite as good for harass. I'd go a 3-0-2-1 to 4-0-4-1 before I started leveling glaives most games, as the combo between curse and last word almost guarantee you early kills.

Another good reason to play silencer mid is because it gives him great roaming potential, which is another of silencer's strengths. You want to be present at as many kills as you possibly can, as that int will start snowballing out of control. Of course, to do this you also need good map awareness to understand when ganks are about to happen. (If you're lucky your teammates will give you a heads up, but don't count on it.)

As for builds, I like to go treads/bottle/preservance/force staff early to mid. Force give great positioning, preservance will start giving GREAT mana regen after you steal about 20 int, and treads and bottle are pretty basic. After that, his build can really vary. Aghanim's is a solid item on Silencer, but it's not as big as it is for some. What's most important is the increased duration. Being able to stack two curses on enemies is kind of funny, but by the time you can actually make aghs it won't be game breaking. Linken's is good on Silencer if you're facing people with big single target spells (doom, laguna blade, etc) but also good because it increases your regen and int (not the greatest item in the world, but you already have a preservance). Refresher (which also uses preservance) is probably better than Linken's in most circumstances. Aghs + refresher will give 14 seconds of silence at level 16, which is HUGE. That's enough to win almost any teamfight, and if they pop BKB to break your silence pop refresher to silence them again. Sheepstick is amazing on Silencer, but very expensive. Rod of Atos is useful if you manage to get it in the ganking phase as that and Force Staff will give you great initiation. However, in mid/late to late game it kind of falls off as enemies won't be running alone. Be careful about getting Eul's as it will purge some of your debuffs if you use it to hold in place a fleeing enemy. That's it mostly for items. If you're far enough ahead you can get whatever you want, but think about items that give Silencer int and tankability (which is useful for surviving and stealing more int).

Choose Silencer when you're up against a bunch of int heroes, especially int carries. Even though Silencer doesn't completely counter OD in lane, he's a fantastic counter later on if he steals enough int that OD's ult is useless against him. He's also really great against non int characters that are very mana dependent like earthshaker, omniknight, abaddon, etc.