Building small garden walls are well within the range of doable DIY projects that can be completed by the homeowner. Retaining walls on the other hand require engineering and special consideration of site conditions and surcharges, which may be out of the scope of what most homeowners can handle on their own. We firmly recommend utilizing the installation instructions provided by the manufacturer of the specific wall products that you are installing.
The key to successful retaining wall construction is a level foundation of blocks. Your wall will be much easier to build if you start with a level base and level each additional course as you go. The foundation course must be partially below ground level so that the soil holds it firmly in place.
Barkman and Rosetta Stone wall installation instructions can be found here.
Belgard wall installation instructions can be found here.