Well, you can't "put" it there, exactly, but you can leave it there.
Nah, there's never much problem with grass on Long-Hop\Half-Volley length - even if a ball moves from Long-Hop length, good batsmen have still got easily enough time to adjust. And if something lands Half-Volley length, it doesn't get a chance to move.
The bat hits it before then.
Personally - for Test-matches - I like best pitches that are relatively quick and offer a reasonable degree of seam-movement. The best bowlers will still bowl economically, and the grass means the seam will grip and the bounce means edges have a good chance of carrying. Inaccurate bowlers will get less deliveries to seam and be more expensive. I don't like super-quick pitches like sometimes get produced at The WACA because they turn useless bowlers like Lee into relatively dangerous ones - they make it possible to beat batsmen for pace and bounce, and I've never liked that. Still, as long as they're confined to The WACA - and they are - it's not too bad. Equally, I really don't like pitches where the team batting first just piles-up 650 and the next team collapses for 400 in 2 digs - there's nothing more boring. Nor do I like it where you get 500-plays-500 - equally boring. I certainly don't like win-toss-win-match pitches (ie: ones that offer seam at the start - team stuck in gets knocked-over for 250; team batting piles-up 500 as the pitch eases; then it starts to take spin and team gets rolled-over for 250 again).
There's always got to be some spin-friendly pitches - it's essential to maintain the fabrics of the game - but I prefer it when they're mostly confined to the subcontinent.
For ODIs I like a relatively slow pitch, making accurate 75-80mph bowling difficult to get away but quicker, more wayward bowling easier to seize on. Where bowling standard-good-length then bowling in the blockhole gives it's rewards, and where looking to take wickets will often be punished. I don't like it when it gets too slow and you bring average fingerspinners into the game and make it one of those dreadful reversed matches where the 15 overs are a hammer-tongs and then it gets harder and harder as the ball gets softer, and I don't like it when you get an easy-paced belter where it's really, really hard to bowl economically unless you're landing just about every ball on the same spot. The more consistent the better, too, as wicketkeepers can trust it - the more the wicketkeeper stands-up to the stumps to the seamers, the better.
Above all, though, whatever the pitch, I like it to stay the same throughout the game. Obviously a pitch will very, very rarely change over the course of 100 overs, but in Test-matches you see pitches that change sometimes. Again, that gives an unfair advantage. What is great, though, is pitches like Headingley where it's a lottery - batting can get quite easy when the sun's out, but when the clouds come over the bounce gets uneven and it starts seaming. They're great, though, only as long as they don't occur too often.
