A really gentle shampoo so it cleans your hair but doesn't make it 'squeaky'. You only need a really tiny amount and only need to apply it to your scalp (as it rinses through the rest of your hair that is kind of enough). If you shampoo the ends and / or if you use a harsh / astringent shampoo (as many supermarket brands are) then it will tangle...

Pantene works for me. Aveda damage control works great, too, but it is expensive in comparison.

Then LOTS of conditioner (until it isn't absorbing any more). If you leave it on for a couple minutes to absorb and then run your fingers through it it should detangle... I have this thing about changing brands every couple washes but that might be superstition...

Tigi catwalk does a really good leave in conditioning treatment. Helps soften / detangle. I have this keratin spray at the moment that helps with that, too... My issue is more about flyaway hair (that goes NUTS if I try and blowdry it and I really don't want to wreck it by assaulting it by pulling it with hot metal) and tangling is kinda subsidiary to that, I think. Also tangles more if the ends start to split so regular trims can help... And if you are breaking it when you try and detangle then that will damage the ends so... More tangling...