From sneezing to stargazing… from breathing to sex anything can be used for meditation. Meditation is achieved by making your mind anchored to some perceptible aspect of the tangible realm. By the way it is not about ‘concentration’ rather just ‘relaxed yet continuous awareness‘ on any chosen anchor.
If someone wishes to know what are possible anchors and methods in meditation then the only book I can recommend is Vigyaan Bhairav Tantra because it is a book which contains all the possible meditation anchors. The techniques herein vary from very simple to extremely complex ones. Some techniques are so advanced that they are not suitable for today’s man/woman.. probably human race will take few more centuries to evolve enough to even attempt those.
Although it is the job of a Master to choose a meditation for you however if one feels that surrendering to a Master is not appropriate for one’s intellectual stature and ego then (despite of all the dangers of being stagnated at ‘feeling great’ without any pragmatic transformation through it) the only choice left is self-experimentation. One can experiment with these one by one to find out which technique works for you. To begin with try any meditation technique for minimum of 121 days before discarding it for the next (if that doesn’t work for you).
One last thing (all Tattva Shakti Vigyaan
practitioners know this!) which must be remembered as it is the most important point. Keep in mind that there are some preparatory processes for meditation
too (most of the people are just not ready for any meditation) and those should be also perfected before jumping on to meditation mat.