I clean my objectives with a microfibre cloth, and sometimes some isopropyl for stubborn stains. You could use meth as well for really baked on stuff.
If it's quite dusty, get something like a lens brush first to get rid of the main particles, then blow air across it with a rocket blower or something like the Hurricane canless air system. Then use the microfibre cloths.
it's very much like doing your car with a foam wash and two bucket method: you want to ensure all the "big" particles are gone first with the foam wash, because rubbing these against your pain will scratch the surface and give you swirl marks. Then you go at it with a microfibre cloth and two buckets to ensure no contamination gets into your clean bucket.
Obviously you can't use two buckets here, but you can use two microfibre cloths
So wipe no more than two times across the objective, then use another side of the cloth to finish off or another cloth.
Pec Pads are also a great thing to have on hand, I have been using them for 20 years on my photography gear.