Purely scientific? Depth of Field Calculator. There are many in browser available via phone. Will show what is area(by distance from sensor plane) is in focus at every distance for every aperture and for every focal length for every format.
Aesthetically? Lens Tests. Depth of Field Calculator is great, but won’t tell you about focus rolloff, or bokeh size differences.
Testing can be tedious, but depending on the subject/compositions you plan to use often and the focal lengths available you can focus on that. It’s even easier if you can shoot video with your camera - slap on a lens, light a subject with maybe some foreground/background, mark distances to subject from different camera points and roll for 10 seconds, keep rolling and change the aperture every time. Change iso or light intensity to compensate for image viewability.
Lastly, something small to leave you with - lenses are (typically) designed and calibrated to have the best performance between t/2.8-4. Nothing wrong with with shooting at 1.4 or 22, but the closer you are to those stops the less vignetting, aberration and other unpredictable elements you will find.
Practice. Practice with video or live view is best. If you can track someone/something in focus for seconds-minutes, you can probably grab it quickly for a single shot.
Use the distance markings on the barrel. Carry a tape measure and play the distance game when you’re not shooting(How far am I to this window, window to sink, etc. etc.).
You can also set focus to a certain distance for a frame you may want, and when walking about take your shots at that distance…used this method for street photography with a very troublesome old film camera.
Use a Depth of Field Calculator and understand the throw of your lens + depth with chosen aperture and sensor size. Typically, your throw is longer the closer to the sensor and much shorter for distances further away(1’-4’ might be quite a difficult focus movement if you’re framing up quickly on the street…10’-30’ is likely pretty small and fast).
Focus magnification is your best friend on a digital camera, ideally on a button you can easily press while looking at viewfinder/monitor. Peaking/focus magnification isn’t very reliable(false positives, etc.). Shooting in a view/monitor that displays black and white also anecdotally helps(the contrast increases ability to perceived sharpness, which color can distract from and make sharp edges less neat. I personally find it helpful).