Having tried and experimented with a moderate variety of pre-workout supps, I feel like I could share some wisdom:

::edited to include links to some sources::

• Caffeine (any generic caffeine pill or coffee works)

I feel this is an essential part of just about any pre-workout, it improves focus, motivation, and increases endurance. 100-200mg dose is my preference. It can be a powerful, stand-alone pre-wo supp or work synergistically with the others.

• Beta-alanine (a decent deal from smartpowders)

Great for endurance, 5g pre-wo gives me the slightest paraesthesia but is great for my 2h+ weekend workouts (which usually includes complexes, followed by endurance work on the Erg or swimming).

• 1,3-DMAA (capped source here)

Dimethylamylamine... the stuff in Jack3d. Great focus enhancer, but isn't fantastic in motivating me to lift heavy or for many sets unless paired with caffeine. I find myself a lot more irritable on DMAA and often catch myself mentally critiquing people's lifting form at the gym while under this one's influence. 40mg of DMAA + 200mg caffeine can be a beastly dose, however, if taken on a relatively empty stomach.

• Choline citrate (or bitartrate), DMAE, Alpha GPC caps or bulk

I haven't been overly impressed with any of these acetylcholine concentration affecting as pre-workouts, but without excessive CNS stims in my system, they do have an effect on my focus in the gym. I would categorize them as very mild unless paired with a CNS stimulant (or piracetam for focus, which I've started only recently and don't have a lot of self attributed data on).

• BCAAs (Xtend, Generic unflavored)

CNS stims work best on an empty stomach, the studies indicate BCAAs' effectiveness at preventing muscle breakdown in a fasted state while strength or endurance training. I cannot comment objectively on the efficacy first hand, but 2-3 scoops of Xtend is a staple if I workout completely fasted, and the citrulline seems to slightly help with endurance.

• Creatine (SP Creatine Monohydrate, TrueNutrition)

Although I don't usually take it as a pre-workout (due to usually working out fasted and my preference of pairing it with carbs), 3-5 days of continuous supplementation with 5g/day (during any time of day) shows noticeable improvement for lifting. If taken pre-workout, I like it for my longer non-fasted workouts in a 1:1 ratio with beta-alanine and choline/dmae for some focus. About taking it with caffeine: it doesn't seem like caffeine completely negates creatine's phosphate donation and whether you want to avoid the slight inhibition is up to you.

• Ephedrine HCl (vitamart.ca - a Canadian place based in Edmonton, Alberta, I do not know if they ship to the US)

This is the fucking king of CNS stims and adrenaline/noradrenaline precursors. I know that it is primarily used as a cutting supplement for appetite curbing and stimulating thermogenesis, however, I'll be damned if I haven't broken all kinds of lifting PRs on this stuff paired with caffeine. It, of course, comes with a whole set of disclaimers and one should use it with caution (e.g., don't go out and do HIIT on it). But a 25mg/200mg Ephedrine HCl/Caffeine dose 45-60 minutes before a lifting session does wonders for my motivation, focus, and CNS employment - more so than anything I have tried.

Stacking:

I prefer to keep the ingredients of my pre-workout combinations limited depending on my goals for the workout and how I'm feeling.

• A hard lifting session usually calls for strong CNS stimulation and focus, so Ephedrine+Caffeine, DMAA+Caffeine, +Beta-alanine, +Creatine as per preference.

• A more endurance based workout usually calls for something like choline+dmae+beta-alanine in approximately 3g/3g/5g proportions, but this can be experimented with. This seems to go well effects of caffeine still lingering in the system (e.g. having a coffee 2 hrs before the workout, and having the stack 30 minutes prior to workout).

• Before soccer I often want the focus from caffeine and the added endurance from beta-alanine so will often pair them in a 100mg/5g ratio for great effects.

I am currently experimenting with piracetam as a focus and study aid and plan on giving it a shot prior to working out. So far its effects haven't impressed me entirely, but reading some reports in /r/nootropics makes me believe i need to be patient with this one.

I hope someone finds this useful and if not, I don't mind having reflected, in writing on some of the supplements I've experimented with in the last 6 months.