Hi all

I have to agree with IanS. Get your levels as high as you can without distortion. Good tape (I used TDK with my 424mkII) will saturate nicely and is quite forgiving (unlike my new digital thing which has to be spot on or it clips).
I bought a small Makie mixer which allowed me to route through a compressor and effects unit. The compressor can help even out the signal and let you record hotter. The effects were mostly used on mixdown but it is nice to have a little reverb in the monitor mix when recording.
A good mike helps a lot, having said that I had great sound from a couple of cheap Behringer mikes and a small electret mike worked well on acoustic guitar.
With IanS again, keep the heads clean. I used to clean every session as well as demaging the heads (I used the cheap cassette type demager which some say doesn't work but I never had any problems with drop out).
Have a look at the following they may help

homerecording.com
homerecording.about.com/musicperform/homerecording/library/weekly/aa041900a.htm
www.ozemail.com.au/~opmnet/guideh.html

Have fun
Gary