To the OPs credit, there really aren't an abundance of good soma (carisoprodol) information threads.
As others have said, start out with one or two of them. Soma can affect people very strangely. One day the same dosage might do almost nothing, the next day you might be so affected you cannot walk well.
One important note is that carisoprodol oddly lowers your seizure threshold. I've seen it said that this becomes a real risk when taking 5 or more per day. Also be careful taking it for something like an amphetamine comedown, as amphetamines already lower the seizure threshold and soma can make this worse.
Carisoprodol is addicting, and withdrawals have been compared to that from benzodiazepines. Carisoprodol is metabolized into meprobamate (brand name Milltown), a known drug of abuse and dependence. Contrary to common thought though, carisoprodol is active on it's own and is responsible for most all of the effects felt after taking it.
Because of the quirky nature of this medication, I'd reccomend taking a lot of caution combining it with alcohol or any other drug. I took one of them with my normal opioid dose and was rendered absolutely useless for some time, so it greatly increased the effects for me.