Cross Stitch Questions

I've only ever attempted one cross stitch project before and that was years ago. It was a white cat sat in a bed of pink flowers and I got so fed up of all the white that it never got finished. It must have been well over thirty years ago, though I've still got the unfinished project in my sewing box but I can't remember much about working on it to be honest.

After seeing lots of pretty cross stitch projects on blogs, I quite fancied having another go so Mick bought me a kit for Christmas. Isn't it lovely?

The problem is, I don't really know where to start. I have lots of questions so I hope that some of you can help. Firstly, is there a particular way to stitch, i.e. top to bottom or left to right, changing colour as you go, or do I complete everything in one colour first before changing to the second colour, or do I complete different parts of the picture such as the roof, then the door, then the windows etc.? Do I need to use an embroidery hoop? How many strands of thread do I use at once, I seem to remember using two strands together?

I'm sure I'll have lots more questions once I start it. If you can think of anything else I might need to know, I'd be very grateful for your help.