I maintain a spreadsheet of certificates on order
Name
Surname
Spouse Name
Spouse Surname
Type (B/M/D)
Year
Quarter
Vol
Page
Date Ordered
Date received
Notes (things like "might be this one or might be xxx, 8a, 123"; "should be the wife of xxx", and after receiving them "not mine"; etc.)
I find it less wasteful than printing out the confirmation page and I can also instantly check that I've not already ordered the same certificate (which has been known ...)
The downside is you see how many lines are in the spreadsheet and hence you can all too quickly see how much money you've spent on certificates!

Now I'm in the habit of never ordering a certificate without adding it to the spreadsheet, it's working very well for me.