So you want to write Faith/Lindsey fic, huh? Good for you! This coupling needs all the writers it can get. There are a couple of things you should keep in mind, though:

Faith went to jail. Now, it's prefectly ok to have her elsewhere in your stories, but don't leave her freedom unexplained. Did she break out? Has she paid her debt to society? Did someone else have a hand in her release?

Lindsey has two hands in anything set after 'Dead End' or before 'To Shanshu in LA'. However, between these two episodes, (ie. every episode he's in save for 'City of', 'Five by Five' and 'Blind Date') he's got one real hand and one prosthetic.

Faith and the scoobies parted on bad terms. As with Faith being in jail, this can be remedied easily but should still be explained. Same goes for stories that have Lindsey working with Angel, Cordelia, Wesley and Gunn. Why are things the way they are?

Of course, the easy way to dodge that question is set your story in an alternate universe. But if you choose to go that route, keep in mind that your characters still have to resemble the Faith and Lindsey from the canon. Otherwise you might as well write original-character fiction.

On a positive note, both Faith and Lindsey are prone to transience, so pretty much any location you feel like putting them in will be plausible. Still, as I've said before and I'll say it again, it pays to explain anyway.

Have fun writing and mind the evil hands and wicked painful knives.