For some projects you may need circular or cable needles. Many people find that all yarns stay on substainable wood better than metal or plastic needles. Experiment to find out what works best for you.
Some projects will require you to work to a specific gauge (tension). Details of this will be included in your pattern. It is a good idea to knit a swatch of 10cm-10cm (4x4in) in stocking stitch (stockinette stitch US). These swatches are helpful if you are doing the pattern in an alternative yarn/wool suggested in your pattern.