So.. Hello guys. My Name is Jinguzi & I'm a 1200 Elo player on EUNE.
I've been playing all roles. Top -> Mid -> Jungle -> Bot lane.
But I've had quite some experience on every single lane so far. Feel free to ask me anything in the comments.

Pros
High CC
Mobility
Can do great ganks with E
Her R.
Great escape with E

Cons
Squishy Early Game
Long Cooldown on W & E
Low mobility when E is on CD
Low Mana Reg Earlygame

I run 21/0/9 masteries as a usual AP Caster. There is a version of Lissandra making her abit tankier with more sustain and hp. Incase you are going that build you should try 21/9/0 or something similar. I guess there is not alot to talk about at this Section.
Remember you can always play around and find a mastery suiting you.

The runes I run is normal Ability Power Runes with some Scaling MR. There is always a change you can do for example using Health Yellow and AP Blue. You'll have to mix by yourself to find a suitable rune page for just YOU.can run something else if you want. For example health Seals but then you would use something like Glyph AP or something.

So. Incase this is your first time playing Lissandra you might wanna check this video out before doing anything else : http://www.youtube.com/watch?v=xsCp5lBceTA

So. There is 2 options here. Either start Maxing Q cause of Poke & Slow. Or you can start by maxing W for the extra root time. In my opinion you should always go with W first. The root time is in my opinion better than the slow and W is way more handy in teamfights.
There is always a scenario either using the ulti on yourself or on your enemy. You should try think & stop for a second to look for examples where you can save someone using your ulti.

There is alot off different ways to enter a teamfight with Lissandra. You can use E followed up by W R then last spam Q. There is also ways like poke with Q then enter & finish with E W Combo. You must try yourself what suits you but in my opinion E,W,R,Q Is the best combo. If you use the ulti on yourself you'll note it is the same effect as Zhonya's Hourglass

So starting off with Faerie Charm Pots & Ward. Fine you're not a support but those health potions and the Charm can help you stay in lane and farm for alot longer than your enemy. You should get Haunting Guise before T1 Boots incase you can afford it on first recall. Else start with Boots and then upgrade a Liandry. After Liandry everything will become way better. After that you should get T2 Boots followed by a Deathcap. After that upgrade the Faerie charm you had since start into a Chalice Harmony and soon after that Athene's Unholy Grail. After that you can either get Rylai or Guardians Angel depends on how hard you are getting focused. So last Item will be whatever you didn't buy before & of course don't forget your Enchantment Homeguard. In my opinion homeguard upgrade is one of the best upgrades for any AP Caster. When you go back to B you have full hp/mana after around 1 sec and your movement speed boost is great for coming back to maybe a teamfight or Baron