I have a newbie question from a newbie player. (thats me lol) i'm getting something like a rust/dust build up on my strings that get all over fretboard also. does anyone know what it is? does anyone have this problem? am i suppose to polish my freboard to stop it?

i play at least 45 mins a day. help? i clean it every week.
The oils/dirt and grime on your hand rubs off and gives you that black grit on your strings. Everything from that bit of dirt when you opened the front door to that peanut butter & jelly sandwich you had for lunch collects on your fingers. Once a week isn't enough if you play every day, make it every other day.

Get a plain white cotton rag and a little dot of 3-in-1 oil (about $5 at any hardware store) and wipe down each string after you get done playing. Another thing that helps is washing your hands each time before you play, so there's less dirt and oil there that can build up on your strings. It'll make em last longer and sound better. Also, a little dot of 3-in-1 on your nut, bridge, and tuners where the strings contact will help to avoid snapping.

In addition, get a polish cloth ($3 - 5 at any guitar shop) and wipe down the body of your guitar also. The same grime you find on your strings will also collect on the body, bridge, fretboard, and anywhere else you touch like knobs and switches. It's a good practice to wipe down the body often, take a cue tip and clean around the pickups and bridge, and to wipe down your fretboard whenever you change strings. If you maintain your instrument it'll serve you well for years to come!
-Guitar Gear-
1995 American Fender Strat, EMG 85 pup
Randall RH200 Head
Marshall 1960a Cab
Woods Acoustic
-Bass Gear-
Spector Legend 4 bass
Washburn Bantam bass
Hartke HA2500
Fender Bassman 410H
Play what you love, love what you play
Wash your hands before you play. Make sure you wipe down your strings before and after you play.

Not only will your guitar or bass stay cleaner, but your strings will last longer.
.sometimes humidity levels can create problems.

I once lived in an apartment where i had to get a tree to control the humidity in one
of my rooms.

Its most likely just oil from your fingers tho.
I bet Charlie Brown's teacher's name was Mrs.Hammett
Its probably oil and stuff from your fingers, i have a nice acoustic\electric
The Takamine EG341SC, and everytime before i play it, i wash my hands, the dirt and other junk on your hands will get on the guitar, make fingerprints, and make the fretboard and strings dirty.

So just wash your hands before you play.