My 2 cents after spending time climbing with some very experienced ice climbers:
1. it was kind of mentioned, but if possible place screws at an upward angle - 10 degrees, not horizontal.
2. T-slotting a screw through a hole in the ice is a BAD idea. You'd be much better off putting two holes in and slinging it.
3. although i'll take some flak for this, other than for protecting the belay (first placement or two after the belay), screamers can be overrated. I've heard of good reasons why they can even be bad in some situations (specifcally for ice climbing), but i can't recall exactly why. But it made a lot of sense at the time and came from some very well respected climbers who now rarely use them. I'll see if i can find the info. The BD website also used to have a really good section on ice placements - they may still.
4. I also take some flak for this, but we did a number of test falls (using a dumby) on good to shitty ice and although it was anything but a controlled a scientific experiment, it was very surprising just how well screws held, even in what I would consider shitty ice. Not that this should encourage you to throw caution to the wind, but i was shocked at some of the falls that held.
5. but mostly, i'd stress what the other have, look around, be creative - find something decent, even if it means downclimbing a bit to find a better placement.
6. ps - for ice climbing buy the ropes with the lowest impact force. While you do open yourself up to longer falls, it can make a huge difference. Probably more so than any screamer would.