Here's a little example:
rem Program Settings
Sync On : Sync Rate 30
AutoCam Off
Hide Mouse
Make Matrix 1,1000,1000,20,20
rem Create Player
Make Object Cube 1,50
Position Object 1,100,0,100
Set Object Collision On 1
rem Create Ladder
Make Object Box 2,100,500,20
Position Object 2,500,250,500
Set Object Collision On 2
Position Camera -100,0,-100
rem Main Loop
Do
If Object Collision(1,2)=0
If DownKey()=1 Then Move Object 1,-5
If UpKey()=1 Then Move Object 1,5
EndIf
If RightKey()=1 Then Turn Object Right 1,5
If LeftKey()=1 Then Turn Object Left 1,5
PX#=Object Position X(1)
PZ#=Object Position Z(1)
rem Gravity
If PY#>0 and Object Collision(1,2)=0 Then Dec PY#,5
PAY#=Object Angle Y(1)
GoSub Check_Collision
rem Update Player and Camera
Position Object 1,PX#,PY#,PZ#
Set Camera To Follow PX#,PY#,PZ#,PAY#,500,PY#+100,50,0
Sync
Loop
Check_Collision:
If Object Collision(1,2)=1
If DownKey()=1 Then Dec PY#,5
If UpKey()=1 Then Inc PY#,5
EndIf
Return
It's not the best example there is, but it works

. If you have any questions just ask

.
@NanoBrain - Math would be better, but thats really only needed when the levels start getting really complex and you start worrying about speed.