If you leave tracts outside, ask yourself, will they blow away? (You could place a stone on them or use a heavier type). Will it rain today? If I leave them lying around late in the evening will they be thrown away by the cleaners (maybe the cleaners will read them!)
If you are going to hand them out on a street, make sure you go with someone else, and if you are young, take an adult with you.
If the tracts have a church contact address on them, then ask those responsible if they are happy with you to leave them around. If not, consider buying your own.
I personally have a special e-mail address stamped on the back for people to contact me. Many tracts already have a reply address on the back, like the 'Open-Air Mission', which are my personal favourite.