1, for mic placement, if you're only working with one stereo mic, place it in the middle of the room, since the bass that builds up along the walls and floors can make your recording muddy. Position closely and point the mic directly at the source, if you have multiple sources then back the mic away to capture more area. You'll have to worry about reverberation in the room, so go to an area with the most sound absorbing properties, ie usually where there's carpet.
2, record the highest setting possible. Always record in an uncompressed format such as wav. Use 24bit 44khz if possible.. If you can only go up to 16bit, record at 96khz. If you're stuck with 16bit 44.1, it's usually no big deal, but you lose alot of headroom and get more noise when using compression.
3, if the volume is inconsistent throughout the track, simply turn up the volume of the soft parts in your audio editor (audacity?) or apply compression or normalization. Remember to make sure the recording doesn't peak, record a few dB below your highest peak to avoid that issue entirely. If you're recording in 16bit, you can't have the gain down too low either or it will introduce hiss and distortion into the track, in tiny amounts so you may not notice it at first.