What version of logic are you using? I find the best thing to do is make the audio sample as big as possible so you can see the waveform and where you want to cut it, then if you press 'escape' a little toolbar should come up where you can select a 'scissors' tool. From there mate, you just start cutting it where you want. If you want to time stretch the sample, double click on it so a separate window comes up, then go to functions and select 'time machine' (i think thats what its called? It has 'time' in the title), from there time stretch to what you want. Im not the best at explaining things mate so if you need me to elaborate or make it clearer let me know. hope this helps!