Just throwing in my advice after a few years of GHB usage. I've read some great information on reddit and it has helped me a lot when I first started doing G. Look at others advice and remember: What works for others might not work for you. Be responsible when you take G.
GBL hits hard and fast; there is science behind this. I'm a large guy, 6'2 and 235 lbs, so I typically dose at around 2mL every 2 hours when doing GBL. I wouldn't recommend dosing more often. Physiology and body size should all play a role when you're deciding your dosage. I have a female friend who is small and skinny and I typically give her around 1.5-2mL when I dose her. Do your research and START LOW if you're trying for the first time. Even if you don't feel it within the first 30 mins DONT REDOSE. Wait it out and use a slightly higher dose when it's time.
GHB however hits me slower and not as intense, but I think GHB (for me) is more dangerous. I typically do an initial hit of 5mL first then dose 3mL when I'm starting to come down. In my experience GHB is more dangerous because I'm able to function better and have found myself dosing at work because of this. GHB 24 hour dosage sounds hard to achieve initially, but it can sneak up on you QUICKLY. Wake up in the morning and feel tired? Have a hit. Starting to feel low during the day? Have a hit. Come home from work and bored? Take a hit.
Dose timing: ALWAYS set a timer. I have some friends that will take a screenshot on their phone every time they dose. I prefer to start the stopwatch feature on my iPhone and hit the lap button every time I dose.
Hangover/Recovery: I have experienced panic attacks and depression when stopping after dosing for 24 hours (even if I only dose for 1 day). If you've dosed 24 hours for more than a month, this can be dangerous, and some people need medical intervention to help with the withdrawal.
GHB v. GBL: GHB typically is more of a viscous liquid, flows slower, and has a soapy/salty taste. GBL is similar to water consistency and has a chemical taste. GBL hits hard and fast, typically within 15 mins. I personally like the GBL high better than GHB, however, I can function better on GHB.
Dosing after you eat: When you eat before/recently after dosing, food will prevent 30-40% from absorbing, so you won't feel it as much. I typically take my first dose on an empty stomach.
MOST IMPORTANTLY: DONT DRINK ALCOHOL WHEN DOSING. This is incredibly dangerous and I've seen people fall out HARD when doing this and end up in the ER.
G is a wonderful drug (probably my favorite) as long as you're responsible, do your research, and follow the basic guidelines.