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Tony, if the secondary mirror is correctly positioned under the focusser (using a long sight tube is best), then using a laser is a convenient way to complete good collimation. I prefer the style with the viewing window on the side and the 45 deg angled surface to see the returning beam. Then it's a two step job to adjust the secondary then the primary, being able to see the results of your adjustments in each case.
Laser itself need to be collimated (check it bu projecting from a "V block" to a wall say 4-5 metres away, then rotate and see if the bean stays in a tight circle. Secondly, laser needs to be a snug fit in the focuser/adapter. I have a layer of "contact" around the barrel to make it a tight fit.
Many prefer a cheshire collimator to a laser. Many use a technique called a barlowed laser which improves accuracy. I have both and often use both to check final collimation. It's always good enough for what I want, after simple laser collimation.
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