If visiting Tokyo, you have no excuse not to try the original karaoke at least once during your stay. The ideal way to go about doing this is finding a group of locals who will recommend a place to go and probably take you there, offering to pay for everything including all the food and drinks that you can consume.
There are two types of places where you can induldge in the delights of public humiliation; either a karaoke box, or a snack bar. Snack bars are usually relatively expensive, but you get to watch and listen to people outside of your own group performing, whatever this may mean, and "free" snacks, which means they don't take money for the actual food but there is a table charge.
Karaoke boxes are rented so to speak, and you get your own little room with your group, where you can order drinks and snacks, and are provided with a fat catalogue to choose songs from. Most of them will be in Japanese, but a lot of karaoke boxes have a less substantial (though sufficient) English section at the back, containing classics such as Abba (Dancing Queen being a favourite) and the Beatles. Try the "sour" drinks, which are really just alcopops, or the cocktails that they offer. I particularly like the lychee ones, though I did have some creamy green stuff the other time that was pretty interesting, though it's possible I'd already had a few by that time so it might actually be pretty dubious. At your own risk!