I use this set-up:
9 offense into Crit, Improved Exhaust, CDR, and 1 Ar Pen
Exhaust + Ghost
Ar Pen Marks
Flat Armor Seals
Ideal Build: Ghost Blade, BVeil, Merc Treads, Randuin's, Stark's, BCleaver
End stats of around 200 AD, 1.8 Atk Spd, 150 of each defense, 2.8k~ HP, 29% CDR, and 37 Ar Pen before auras, actives, and steroids kick in.
Once those activate, I'm clocking 2.5 Atk Spd, 200 Defense, and 105 Ar Pen.
Then factor in elixirs.
Of course, that's an ideal scenario.
I tend to build in this order:
Negatron + Chain Mail (Order depends on who's kicking my ass)
BCleaver/Randuin's/Bveil/Stark's depending on what I need and what I can afford.
I prefer soloing mid as Xin if my Jungler's competent. Duoing with some hard CC if not.
Soloing mid is very interesting. Some champs, you can dominate, such as an Ashe Pre-6. Just jump in and TTS her when the minion count is low. Others, such as Brand, are a lot harder to fight because of their constant hard CC and burst damage threat. Usually, if you have a decent jungler, you just wait for them to bush camp then TTS to bait a flash. Back off and wait a bit, then do it again for a kill.
Success usually depends on how threatening you seem. Make yourself seem weak and scared, and you can dominate the enemy when they start taking risks to injure you. Just remember that his Charge is also an escape skill for skill shot evasion.
Side lane should be simple. Wait for your partner to CC something then jump in and TSS combo for a kill or heavy damage. Don't be afraid to actually jump in for a quick TTS if they've just blown their hard CCs and minions aren't around. Abuse bushes to scare people.