From my experience and what I have read, root tips are not good explants (unless they are from plants in sterile media) as they are higly contaminated with bacteria and the surface sterilization that will get rid of all these bacteria will also kill the explant. Leaf tissue can be used as expalnt but it will need a lot of hormone adjustments to develop back into callus. The best explants are the meristems itself. For sympodial orchids, you can get it be hetting a dormant bud from the old pesudobulbs. In case of monopodials its a bit tricky as you mav have to sacrifice the plant as the meristem is in the growth tip below the developing leaves. Lastly multiplication on a solid medium is possible but it will give you less no. of plants per explant than the liquid culture wit rotary shakers. My serious recommendation would be to not try meristeming if you are a beginner which you appear to be. I would recommend you start with node cultures of Phals and then proceed with seed sowing. These will help you get started and experienced in sterile techniques, secondly the explants are not costly and will not damage the plants and both nodes and seeds have a predetermined development so treatment with hormones will be next to minimal. Hope this helps you get started. Also read a lot of books on orchid tissue culture.