Some machines have safeguards built in where the foot has to be up or down (varies) in order to actually make/save some of the changes. So if you make an adjustment and nothing seems to change, try whatever you did with the opposite condition (foot up/down).
The other thing that can make a difference is the needle position, most machines will have some sort of marking on the hand dial that lets you know the correct position. It may be subtle like a screw head in the handle lining up with the center seam of the case, or more obvious with little lines and such.
The biggest help for me to remember is that where ever the problem shows, the fix is the opposite way. So if it is loops on the bottom, it is the top tension that is wrong, not the bobbin.
I've always had terrible luck adjusting bobbin casings... I usually have to end up getting a new one/paying for a service visit. Most of my issues are with top tensions.