Ive never actually pre-planned touching someone, theres usually a moment that feels right to touch someone (ie, after he cracks a really good joke or when hes teasing). You should do whatever youre most comfortable with. Most of the time, I won't touch someone until I feel pretty close to them.
For me, usually when a guy touches me, I wont think too much of it unless he does it a lot. I also factor in how often he touches other people to gauge how "touchy-feely" he is in general. Spots I think are pretty flirtatious and usually arent accidental include the shoulders/arms, thighs and hair (lol I guess that pretty much covers the whole body). Also the length of contact is very important too. If his paws stay on you for more than 2 seconds Id say thats flirting. Stroking also a huge sign he likes you.