I compiled EVERYTHING I know about GHB and prodrugs so you can make an informed decision when using these drugs (apart from dependence and withdrawal aspect).
NEVER dose G without an oral syringe where you can accurately measure your doses, if you don't have one DO NOT DOSE.
You also need to know whether you have GHB, GBL or 1,4-BDO:
GHB: can be any concentration/ml. I suggest starting at 1ml and if you had no effect waiting 3 hours and trying 1.5ml etc, do not redose earlier than 3 hours. GHB either tastes really salty or like liquorice. Duration: 3-4 hours.
GBL: when pure is equivalent to 1.6g of GHB/1ml but can be cut with water so don't assume just because you can take 4ml of one batch that the next batch is going to be the same. GBL tastes like battery acid, it's a solvent so it will burn your mouth undiluted. Duration: 1-2 hours.
1,4-BDO: when pure is equivalent to 1g of GHB/1ml. A good way to test purity is seeing if it turns to gel/crystallises in the fridge as the melting temp is 20 degrees Celsius. 1,4-BDO tastes milder, kind of like melted plastic. Duration: 3-4 hours.
1.5g of GHB might make you feel great, 2g might make you G out. Everyone is different and needs different doses for the desired recreational effect, never redose before the entire duration of the high has run its course. Redosing early is asking for trouble.
A G out is not an overdose, but never use alone and make sure you and your friends know what to do if someone G's out. Check their breathing and ensure it doesn't get too shallow, if it does call an ambulance. Put the person in the recovery position to ensure they don't choke on their vomit.
I suggest taking the drug on an empty stomach so in the event you G out, you won't puke the contents of your stomach up and choke.
G is the most unpredictable drug to use and requires extreme harm reduction and education to be used at all and even then it still is not completely safe!