one mean t test---the p value approach

I dont quite understand how to find the p value of other hypothesis tests including the one mean t test.

Depending on the tails, are there different ways to find them?
Such as a test become something like right tailed. Do you subtract the t value from 1? What if it is bigger then one? What about left tailed and two tailed? Most of the time when I figure put the p value approach. the value is to be to be considered a p value.

How do you find it? Thanks

Mean Joe

TS Contributor
Typical t Table gives you the two-tailed probabilities. So if my statistic is t=2.1318 with 4 df, then the two-tailed test's p-value is .100. If it's right-tailed, then p-value is half that (.050), since t is positive. If it's left-tailed with t positive, then p-value is 1 - half that (.950).