I've got several but will kick it off with this Devilhorse upgrade/modification I learned from "The Big Show" Terry Scroggins.

I just upgrade my hooks on rattle baits and crankbaits.  Don't do much else.  Well I use dye or markers on soft plastic too.

I use tiny zip-ties on all spinner bait, buzz bait, & jig skirts.

double split rings on spoons/flutters

clear straws to keep senkos on longer

remove front treble on small cranks when fishing around timber or want it higher in the water column

I learned this from a friend. Somedays, I'll throw a Alabama Rig for the heck of it. I have Yum Money Minnow Umbrella Rig. Law in Iowa, you can ONLY have 2 hooks in water but I bought one license for extra one hook. So, I snip 2 sharp hooks and make them shorter and put on the swimbait. It's funny because the fish will bite the wrong hook. Most of the time, they will bite on the actual hook. There's 3 actual hooks on the rig. No picture.

Not really an upgrade or modification but I take some 20 wire and cut it about 1/2" long. After putting my worm or craw on the hook a push it straight down through the bait and the eye of the hook. Bend the ends over like a staple. It stops the bait from sliding down the hook after catching a few fish and in turn they also last much longer now.

Here's a couple more...

 

• I add feather trebles to some of my "walk the dog" baits.....
• Take a small glass rattle and stick in my thicker worms like ultra-vibes, ole' monsters and senkos.
• Also, I always insert 2 glass rattles into my Spro hollow belly frogs.  Strike Kind frogs comes with rattles out of the package.
• Depending of the brand of hollow belly frog, I always trim the skirt 1/2"-1" to help walk better and reduce short strikes.  After trimming both ends of frog skirt....trim 1/4" off of one side to make one side a bit shorter and make the frog walk a lot better
• On my lunker lures/buzzbaits, I will bend the shaft so the blade barely taps the wire on occasion to make a little extra noise.  Also, secure the pop rivet on the buzz bait so it doesn't slide and take sandpaper/file and rough up the contact points on the rivet and spinner for extra squeal. And to really break it in...take electrical tape and tape the buzz bait to a car antenna/running light on boat and ride around to get the squeal quicker out of the package