Loose spokes can happen from break-in of wheel sets, a curb strike, a pothole, or running over that yapping poodle the old neighbors with the Cool Studebaker think is their long-dead son... or just neglect. you have chosen NOT to neglect your wheels.... GOOD!
tip #1..:instead of "plucking"spokes, strike them with a screwdriver handle... using two at once creates A Bicyclophone! (Radial lacing works best for this)
check for any extra-loose spokes... bring up their tensions to an OK level first... then go around the wheel to look for any other extra-loose ones... then watch,read, and learn... enjoy!
https://www.parktool.com/en-us/blog/...on-measurement
there are many more excellent Vids on how to do this... unfortunately, there are also some really lousy vids.... Sigh.
Tip#2.. Remove the Tire and tube before you do anything truing-wise.(shop guys do quicky tunes with the tires still on)
work slowly and carefully... one spoke won't solve every problem... and you'll discover that changing one spoke can alter the tension on a completely different area of the wheel.... You can do more by loosening a really tight one than tightening two kinda loose ones, as far as moving the wobbles that you just introduced to your once fairly straight wheel....
(Top Secret tip time!) A big warp to the right will usually have two satellite warps of smaller amounts to the left... work the big warp first...
tip #3... if the wheel is warped more than about an inch out of true, you will usually not get it straight with just spoke-tightening/loosening.
biggest mistake i see is folks wanting to just tighten the holy crap out of one spoke and never even try to loosen one opposite or use adjacent spokes.... followed by rounded off nipples, snapped spokes, and the occasional hack job by twisting sharp angles into spokes to "tighten it up!"...
now.. i recommend Learning on a Cheapo wheel that looks like garbage first...
You DO have a truing stand and/or CENTERING GAUGE, correct? And raunchy Wheel Bearings make the task just that much tougher....... they need your love too, ya know!