Here's what I would suggest in this order:
1. Make sure that your body is calibrated. If you haven't had it CLA'd by Leica or someone you know is good, you should do so.
2. Make sure whichever lens you have that has the narrowest DOF is calibrated. Again, get it CLA'd if necessary.
3. Once those two are calibrated, you have a solid reference point to check other lenses you may buy. Of course, if the body or lens takes a serious bump, you may have to have them recalibrated.
4. Then as suggested by others, practice.
At this point, if after a reasonable amount of practice, you're still having significant difficulty, try a magnifier. Either Leica or Japan Exposures are the only ones that are trustworthy from what I've tried (Japan Exposures) and read.
The bottom line here is that your eyes are your eyes not someone else's. People who are younger with good vision and no allergy conditions that affect their vision find it easy to say you don't need a magnifier. For some of us, magnifiers help. I've tried with and without. On fast 50's and longer, I get a better hit rate with a magnifier. Unfortunately, no one can tell you what's going to work for you. You just have to try it. They are a fairly big investment considering their size but if they don't work, you won't have much trouble reselling them.
One other point about checking focus accuracy. You don't have to have a Lens Align or other fancy equipment. Shooting a specific point on a brick wall at about 60 degrees will allow you to see how the lens DOF falls around the focus point. Take several shots, particularly with the really fast lenses as you will undoubtedly vary your focus some from shot to shot. I do this at about 8 feet but shorter may be better if you shoot shorter distances a lot. If the lens is okay on this test, then have a series of things that are always available at varying distances and shoot them to see if the focus is accurate, particularly near MFD and at infinity. Every time you get a new lens (except for very wide lenses), check it in this way. After you get used to doing this, it won't take long to determine if a lens is calibrated or not and it will save you from scratching your head when that new lens just doesn't seem to be sharp. I had a brand new Lux 50 ASPH earlier this year that came out of the box not correctly calibrated so don't just assume a new lens is going to be right.