Use the DI - and no, I'm not being flippant
Superimpose the runway on the DI as you approach the field. This'll help you ident the runway as you approach as you can see which way the runway will be lying in respect to yourself.
Then use the DI to work out which side you are and whether you will have to overfly the runway - for example:
Rwy 21 with a Left hand circuit - you're approaching from the south (heading 360)
So - 360 is at the top of the DI, the runway runs from top right to bottom left on the DI, left hand circuit so you can see that the circuit direction is actually the side of the runway that you are approaching from.
Solution - overfly the runway and descend on that side.
If the circuit was right hand then superimposing the runway and circuit on the DI would tell you that the deadside is the side that you're approaching from - so don't cross the runway.
Try it - it works every time
CM