Like Pincho said, its good to have a working frame before doing anything. Something as simple as this;
SYNC ON:SYNC RATE 0:AUTOCAM OFF:HIDE MOUSE
MAKE OBJECT BOX 1,10
POSITION CAMERA 0,100,-300
POINT CAMERA 0,0,0
DO
IF UPKEY()=1 THEN MOVE OBJECT 1,1
IF DOWNKEY()=1 THEN MOVE OBJECT 1,-1
IF LEFTKEY()=1 THEN TURN OBJECT LEFT 1,1
IF RIGHTKEY()=1 THEN TURN OBJECT RIGHT 1,1
SYNC
LOOP
That gives you movement, sight, and the main client settings to work with. Now implementing your user model/maps and other code is relatively simple, instead of starting right away with the map models and shooting and whatnot.