duckman -
This is not for the faint of heart but it bust me through a major wall in the deadlift. Easily applicable to squats etc as well.
Day 1 - warm-up lifts (anything less than 80% or so of your max counts as a warm-up here), then about 90-95% of your 1 rep maximum for 1
Day 2 - warm-ups, then 3 reps of the last weight
Day 3 - warm-ups, 5 reps of the last weight
Day 4 - warm-ups, add 5lbs to the 5 rep weight, and do 3 reps
Day 5 - warm-ups, add 5lbs to the 3 rep weight, and do 1 rep
Day 6 - warm-ups, 3 reps of last weight
The pattern should be obvious so I'll stop there. 1-3-5-3 (+5lbs) -1 (+5lbs)-3-5
With the deadlift, you really don't want to do much more than 3 sessions a week if you're pulling close to your max each time. Anything more will be counterproductive. You might find 2.5lbs is more than enough of an increase as well. If you can't make the reps on any given day, either try with less weight, or take a couple of days total rest, then try again.
Also, any time you plateau, it's worth looking at your form again. There's almost always something you can tighten up that will make a difference. Try using the alternate grip for the heaviest sets (see my video a few pages back). Try the hook grip (with the thumb hooked under your forefinger - it's very painful at first with a heavy bar, and you may well bruise the crap out of your thumb but it's incredibly strong).
And of course, rest and nutrition are also going to be reasons for plateauing at some point. Hard for me to say what's going on with you. Simply changing what you do in the gym isn't always enough.
Don't skip the warm-ups - it's essential for proper motor neuron recruitment. Your body needs to get used to the idea that it's going to have to bring everything to bear on that bar before you move to a new PR.