I don't know what this nonsense is about over-muddling mint. Mint doesn't taste bitter at all when you muddle it, in my experience, and in fact to release the oils it is essential to crush it (we have a prolific lime tree, and mint everywhere, and people always love my mojitos). It's easy as pie to make a great mojito.
I use half a lime and probably 10-12 mint leaves (though I honestly never count.. just put in enough). Cut the lime into wedges that are easier to crush. Throw it all in the bottom of a collins glass. Sprinkle a little (this isn't for sweetness) turbinado sugar over this for an abrasive. I muddle the lime, too, as I find it a lot easier and no, it doesn't add any off-taste. Muddle until you get every last bit of lime juice and the mint is well crushed. Add ice. How much ice you put in depends on how heavy you want the drink, really. I know the recipe in my 12oz glasses and I fill them to about an inch and a half from the top. This is where people will get finicky: I make a turbinado simple syrup at 1:1. It's just easier to sweeten with in a cold drink than sugar. I use about 3/4 shot per drink; it really depends on the limes and how sweet you like things. Put the simple syrup in first, then pour the rum. I don't measure the rum, just fill the glass til about an inch from the top (this turns out to be about 2.5-3oz in my glass I think). Finish with club soda, stir from the bottom to the top, garnish with mint. It's delicious and easy.