I have to be REAL CAREFUL. Any tips? 
Form, form, form. I'm over 40 and have been DLing for about 10 years. I too started out with a wonky back from BJJ and a few other things. I used Starting Strength and Mark Rippetoes' vids as my guide and have, thankfully, never been injured. Finally hit 505 @ 200lbs last winter, toot, toot :)
Baconator by TKO
I would find a really good trainer in your area so he a fix any form issues you have. Look for powerlifting gyms in your area.
if your gym has one try using the trap bar. Put's alot less pressure on your back
We don't have a trap bar at the gym I go to so I use the hammer strength deadlift machine. I find it makes a huge difference how I feel when I lift.
Gotta agree with RobinHood. Even with perfect form, if you already have a dodgy lower back, what's the sense in doing deadlifts?
Do a little research online on basic deadlift form...Check out the YouTube series called "so you think you can deadlift?"...breaks the lift down and shows you how to do it properly and safely. Then find the best powerlifter in your gym and just pick his brain...having someone there with you while you lift that knows what to look for is the best thing IMO.
RobinHood - Who said doing deadlifts is good for you? Do you think deadlifts is really the answer to addressing your wonkyness?This. You want to consider the risks and rewards.
I'm sure others will chime in. But I reckon you can do other safer alternatives.
You could try sumo deadlifts. They seem to stress the lower back a little bit less than conventional. Sumo is more technical so make sure to learn proper technique. Don't turn it into a wide stance conventional.
What are your goals. You don't have to deadlift ya know?
Great points - thanks everyone (except the jackass). I want to deadlift mostly because I have bought into the idea that if you don't deadlift then you're a pussy. Stupid I know, but I've already had to give up squats in favor of leg presses. I've tries sumo deadlifts and agree they seem less hard on the disc. Also KB sumo dl but like homeboy said you can't get heavy that way. Anyway, thanks for the posts. Appreciate the different points of view.
My goals are to maintain, maybe even increase, my overall strength. Maintain or increase mobility.
My lower back is shot from working construction. I started doing deadlifts 3 months ago and have never felt better. I started at 135 3x5 and just worked my way up real slow. I'm at 265 3x5 right now and feel great.
And anytime I went up I made sure to take an.easy day after
A good idea is to record each set of deadlifts you do and review your technique.
flemingo - if your gym has one try using the trap bar. Put's alot less pressure on your back
This is what I use. A lot less stress on lower back.
jpt123 - My lower back is shot from working construction. I started doing deadlifts 3 months ago and have never felt better. I started at 135 3x5 and just worked my way up real slow. I'm at 265 3x5 right now and feel great.Damn. I'm taking it slow for sure. 220 x 3 yesterday. Was conscious of my form. I'm guessing if I had to I could pull a lot more, but I'm not fucking around. I want to keep the reps between 3 to 5. 2 to 3 sets. I'll slowly increase the weight.
Trap/Hex bar
You could do partial DLs. I think your back is potentially at most risk in the bottom position.
Start with the barbells mid shin or just below the knee.
My two cents, If you insist on doing DL's I'd say really concentrate on pulling the slack out of the bar as you are sitting into your starting position. Meaning you are already pulling the bar up as you get set, this will help you activate the use of your hamstrings a bit more and lessen the stress on the lower back rather than "jerking" the pull from the start. Rough explanation but YouTube it for a more detailed example. You probably won't be able to pull as much until you become more familiar with the movement but it will definitely help save your back and keep you from rounding your back on the heavier pulls.