The wonderful volunteers at FamilySearch are in the process of indexing the Texas death certificates from between 1977 and 1986. Some of the images are already searchable, but if you can't find what you are looking for, you can also browse the images.
What? Browse over 1 million images?! Of course not, that would take ages. Fortunately, they have been divided into groups and subgroups.
First, the death certificates are divided by year. Next they are sub-divided into month and county, or range of counties alphabetically. From there, they may or may not be in any particular order.
So, to browse for my great grandmother's death certificate, I will choose 1980, then find the March certificates for McLennan County. March for McLennan County is divided between Volume 40 (Kendall - McLennan) and Volume 41 (McLennan - Nueces), so from there I have to decide if I want to start with Volume 40 and search for where the McLennan County certificates begin, or run through the images of this county in Volume 41 first, since McLennan will be the first county in that group.
I'm going to go with the latter first, and if I don't find it there, I'll go back to Volume 40. Happy hunting!