you didn't really specify what you are trying to record.. voice? an amp? hiss can often be minimized by finding the correct balance between the recording input levels on your soundcard (assuming that's what you're feeding the mixer into) and the outputs on the mixer. avoid using any kind of gain boost feature.. hiss should never be a result of the way you position your mic, unless it's from an amp, in which case it will certainly be more sensitive to certain positions, but then, repositioning the mic to minimize hiss will change the sound of the guitar in such a case. an amp just naturally gives off a certain amount of hiss, at least tube amps. In any case as a last resort you can always use the hiss reduction features of such programs as Adobe Audition.. it's not the ideal solution but if it's all you can do to improve the sound, do it, just carefully to avoid too many artifacts.