I took heaps of G back in the day. Good fun. Follow the rules.

No Alcohol.
Wait at least two hours before re-dosing.
When starting creep up to work out your allowed dose, eg, try 2ml, nothing, wait two hours (use a timer), try 2.5ml, nothing, wait 2h+, try 3ml, etc. Most of the girls I was hanging with were about 2ml, most of the guys 2.5-3ml. It took me a while because I was 4ml, but I'm a big dude. Some people seemed to have some tolerance or susceptibility, maybe start with 1ml if you're a smaller stature person.
You can't take more to get higher, you'll just od, it's a very binary effect. Adding another 0.5ml to see what happens is where you get in trouble. If it's happened and you're G'd, that's your dose.
Repeat the dosage testing process with new batches.

The effect itself is like being drunk, euphoric and HORNY. I stopped taking it because I was single and it was simply frustrating.

They used to give out "Say no to G" stickers at warehouse parties. Ravers would en masse slap them on people being stretchered out by paramedics.