Use a gallon sized nursery pot. Clematis like regular water - don't let it dry out. Grow it in the pot until you see roots through the holes in the bottom of the pot. That's the way I've done it and never lost one. I see no advantage for a tin can and can think of several disadvantages. Some people plant them directly in the ground and have success with them. I like to plant them 2" deep in a pot and them when I put them in the ground plant them 4 - 5" deeper.

Excellent advice given by bob414 :-) I have no idea what benefit a tin can might provide but I too would be leary of trying that method - there are pretty good reasons plants are not grown and sold in metal containers!

I agree with bob414 and gardengal48. I'll also throw in that buying Clematis in packages as "roots" is NOT the best way to have success with them.

Then what is the best way to grow then when im first starting out?

Bob suggested a gallon nursery pot. This is what many of us use when we are starting out with either very small starts (i.e., clems in 4" pots) or bare roots (if we can't resist). Use a good quality potting mix, plant the vine deeply in the pot (so the stem is buried about 2" or so) and water and care for through the growing season. By fall, the roots should have filled the container and the vine large enough to plant out safely.

Very small clematis plants are just very vulnerable to the big, bad world :-) Too easy for those fragile stems to get damaged either by critters or mechanical damage, too easy to overlook for proper watering and too easy for them to get overwhelmed or smothered by other, larger plants. Growing them on for a season gives them a bit of a headstart and a fighting chance.

And as you might have guessed, buying clems as bare root starts is a risky proposition. In fact, I'd expand that to any type of perennial. There is just no way to ensure that these have been harvested and stored properly so that roots have not dried out or allowed to rot in a too moist storage medium. If the start is showing some signs of new growth - like some green shoots pushing through - that's a good sign. But pot it up ASAP.