cocaine is not the sort of product u want to buy from an everyday dealer, unless they specialize in that... even then..
*edit* firstly must agree with previous posts definitely get the most out of your coke by having smaller lines - lots of small lines lol JK start out slow, as some cokes can get cut with some yukky cheap stuff so it's not that great and you may feel sick. Often first few doses of charlie can make you feel really cool and fine but like you could spew.. similar to an old fashioned ekkie spew lol but u wont.. at least I never did.
secondly most coke is packed up rather tightly and compressed when its packed to maximize the packaging. Sometimes this makes chopping up the coke rather difficult as when u try to cut it, it will just squish lol. Heat up a plate in the microwave until the plate is very warm to touch, the hotter the better but becareful it does not explode you wont to be able to carry it. Once plate is hot, put your coke on it. (only a little at first if u are concerned) ull find it will break up the coke and allow it to be chopped up much more finely. the finer the better - unless u want rocks sitting up ur nose eating away at your nose tissue!*edit*
2 years ago in Melbourne Australia, a friend bought 10 different g's from all different sides of the state...for research

tested the purity of all g's and the average potency was .2% of the gram was actual cocaine.
This is the reason I would suggest for any first time user to get a full gram to start with. But don't buy it if money is a problem for you, as you will soon find unless the coke you try is terrible, you'll want to do a lot more of it lol. Coke is the rich mans drugs because you kinda don't give a fuck... in a wonderfully fabulous way.
The high is different to pills, speed, mdma,pot, booze and alike. Its the shortest lasting and the most expensive. one of the healthier drugs to abuse though lol it will however kill ur bank balance and ur nose cavity tissue (if you don't stop and pick your nose every so often)
for me when I wanted to try it properly - beside the times id been given lines while out partying on other stuff - i got one gram a room at crown casino lol

and 2 girl friends.. we got high and chatted away - made a gay room service guy feel uncomfortable and sexually objectified and had a blast.
Then a month later i got 3 grams and a bigger hotel room and invited more people.. which turned into a coke party.
Coke parties... ahhhhhhhhh the ultimate way to burn money and brain cells lol you just sit around a big glass table with piles of coke being lined into funky pictures while everyone rambles about passion and cocaine waiting for their turn hehe
white lines... blow away lol