Netherlands

Try to buy all your threads for a specific cross-stitch project at once. Why? Because the embroidery thread is dyed in different dye lots. Hence even if you think that you get a specific color from a specific manufacturer, it can sometimes have a slightly different hue. Most times it is not that noticeable, but to be on the safe side, buy it all at once.

In order not to lose the needles for cross-stitching, you can glue the magnetic strip to the inner lid of the box in which you hold the embroidery threads and other cross-stitch accessories. You will no longer lose them and you will can easily find the right needle.

You can cross stitch on different kinds of evenweave fabric. It may be evenweave linen, Aida cloth, waste canvas etc. It is largely a matter of your personal preference.
Just remember: the number of stitches per inch (or per cm) can drastically change the look of your ready project.
Fabric with a higher stitch will produce smaller and finer designs.

Don't leave the project in the hoop overnight. When you're done cross-stitching for the day don't forget to take it out of the hoop. Your embroidery project needs rest to!
And another important thing. No matter which direction your top leg of stitch is going, but please be sure that they are all going in the same direction.

The easy to keep from losing your cross-stitch needles, is to glue a magnetic strip to the inside of the box you keep your embroidery floss and other accessories.
It is very important to double check your counting. It is called counted cross stitch, isn't it? If even one missing stitch in important area can destroy the project. So please, check your counting before you start the stitching. It's worth it.