Actually one need only go once and for Sifrey Torah, Vivian explained that the old scribal trick (though not for mezuzah or tefillin as it would not be will not be written k'sidran (in the correct order)) is to save up all your Hashems, visit the mikveh and then write them all at once maintaining the correct degree of kavanah (concentration).
The waters in the mikveh are "living waters", which must come directly from natural sources, rain water or springs. The construction of a mikveh is quite complex - suffice it to say, it's not just a swimming pool! For those of you familiar with conversion process, you will know that visiting a mikveh entails total bodily immersion with nothing that could act as a barrier in the way. For most Jews however, the mikveh is not a part of their ritual life and it is entirely unfamiliar.
I booked a session and went along. Normally a convert would be accompanied by Rabbis who wait outside but I was on my own, so I had to do some homework before going about how it all worked and what it all was about. What surprised me most was how small it was. Ruins of ritual baths that I had seen at Massada and a CD-ROM of a 3-D journey through the Temple had suggested that these things were big. Reality was different, but then again how big did it have to be - just big enough to submerge myself completely.
My other problem was seriously halachic. Did contact lenses represent a prohibited barrier? (which indeed they are). I donít open my eyes under water, but without lenses or glasses I generally feel helpless in any body of water. Bravery provided the correct halachic response and I went into the mikveh sans corrected vision.
One submerges, re-emerges, recites the blessing and then re-submerges again. Iím not good underwater and with water streaming from my hair and nose and bad eyesight, Iím just glad that thebíracha is short!