I use the "shooter's ear plugs" from Wal-Mart. Just a couple of bucks and they're on a lanyard, which keeps them close at hand. With my 12" Klock Werks windshield, I get some wind blast right at my ears, so these are definitely needed. I don't wear a helmet unless required to, and then it's a half.
I have found it hard to get a good fit on a pair of plugs over the last 40 years in industry, so when I got serious a few years ago I ordered a variety pack here to try out different ones and find a good fit. What I ended up with is the Moldex Spark Plugs rated at 32db. Then I ordered a lifetime supply for about $15, I manage to lose 4 or 5 pairs each year.
Added equipment was a stage 1 HD air cleaner, a Cee Baileys windshield and a turn out boot heel guard. I also went with the BAL1 tail light MOD. You can never be too safe with lighting. Now I am riding a Vision with minor mods to give me this.
I use the foam ear plugs. Have them in many colors.
Big Hint. Before you insert them in your ears, wet your hands with anti bacterial gel, roll the plugs in your hands. Allows plugs to slip on in and provide a tight fit.
Too late for me. Trying to preserve what hearing I have left. IMO, you ride a Harley for 20 + years, your hearing will need to be digitally enhanced. Good news is that good digital hearing instruments are no longer $10K; now $2K at Costco.
I read the reviews on ear plugs at web bike world - http://www.webbikeworld.com/Earplugs/earplugs.htm - and went with the E.A.R. soft. I got a box of 200 or so for about $40 or thereabouts. They came with a lanyard on them but I just pull it out of each plug before inserting into my ear. Work much better than the custom molded pos I got at a bike rally, which actually tends to amplify the low frequency of my exhaust, when I'm wearing my Bell RS1 full face helmet. The foamies I bought are much, much better, imo.