A few tips to start getting a ridiculously good Mojito going:

Making sugar syrup at a 1:1 ratio of sugar to water (boiled in a saucepan), and using that instead of granulated sugar will ensure no gritty bits in your last sip if you aren't vigorously stirring or shaking this cocktail.

Fresh lime juice:
Juice your limes by cutting whole limes into 1/6ths and muddling them with a pestle or muddler, juicing them but not not to the point you're releasing the bitter oils from the zest and pith of the fruit.

Mint:
Bruising the mint leaves, rather than crushing them ensures you get all the essential oils out of the leaf without turning them bitter. A bonus to this is you get no green bits of mint stuck in your teeth if you're trying to impress anyone with your hobbyist mixologist skills.
slapping them between your palms and immersing them in the drink after you've added the soda is a fail safe way to get around this issue.

Lastly: Ice
Always, always, always top up your glass with ice before adding soda. This will ensure you actually taste all of the lovingly prepared ingredients in your creation, rather than fizzy watery nothing.

:)

Celebrated a friends 30th with a Mojito party. We knocked off 5 bottles of rum that night. Was told later that I sang Like a Virgin by Madonna at the karaoke bar (surpisingly well). Nothing more refreshing on a hot day than a mojito.