We have a big tunnel tent and it's quite miraculous how a tent which we could park the car in (if the door was wider) packs down into a bag that fits under our stairs. So how does it fit back in? Well the first time we packed it away it didn't and it went home kind of thrown into the back of the car. However since then we've managed to work out the two secrets to getting it back in.

1. Get all the air out.
2. Fold it narrow enough for the width of the bag before rolling.

These two gems apply to quite a wide range of tents from what I can tell.

So here in more detail is how we get our Sydney Opera House sized tent back into it's matchbox sized box.

1. Drop the tent to the ground and lay it out so that it's all lying within the rectangle of it's groundsheet.
2. Fold the porch section back onto the rest of the tent and fold so it lies neatly.
3. THIS IS REALLY IMPORTANT - Ensure the front door is unzipped.
4. Fold the tent in half lengthwise, so you have the edges on top of each other.
5. Fold the tent into 3 lengthwise, so that the 2 edges are still on the edge (this stops the metal pins on the edge damaging the fabric of the tent). Having the tent now folded into 6 lengthwise makes it the right width to fit back into the bag (The first time we packed it away our mistake was folding it into 4 not 6).
6. Roll the tent up from the sleeping end towards the door (this forces the air out of the unzipped door which is why 3. is so important). After this first roll most of the air is out but not enough to get it into the bag.
7. Unroll the tent and roll it up again. After the second roll the tent should now fit into the bag (if not unroll and re-roll again).
8. Put the bag on top of the rolled tent (don't try to lift the tent into the bag).
9. Roll the tent and bag over so that the tent is inside the bag.
10. Zip up the bag.
11. You are done!

I hope that helps.

A few things to note. Firstly you can get the air out in other ways, for example you can can got someone to roll along the tent like a rolling pin. Secondly the number of times you fold the tent lengthwise depends on the tent and the bag, basically you need to get the tent to be a long thin rectangle where the short side is the same width as the bag, too narrow and the rolled tent will be too fat, too wide and .... well it'll be too wide for the bag. Thirdly (this might just be something about our tent) inside the bag are 2 straps to hold the tent in, but they are only just long enough. If they were 6" longer you could use them to help get the tent into the bag, but as they aren't, they are pretty much useless and we don't bother using them.