Heathpack, You're asking a simple question for which there are many answers. :-)
Refer to paragraph four of the Introduction to The Cyclist's Training Bible.
The answers to all of your questions about what sort of rides to schedule, or how to approach those rides, depend on your history, current state, aspirations, reasonable expectations and goals.
You've identified Hill Climbing as a limiting factor that you wish to improve on. (You're not alone by the way. It's the one most common limiter for almost all of us. Except a very few natural climbs who make all the rest of us feel inferior.)
To make a poor analogy, that's a bit like saying, "I'd like to major in Biology."
You're at a stage where all of the various aspects that make up affective Hill Climbing could probably use work on.
Because of that and the fact that your goal "A" event century isn't that far away. It's might be a good idea for you to consider a training style that existed before the current trend toward periodization. Back in the old days, riders used to target each of their energy systems and riding styles during a training week. Instead of periodizing and focusing on just one area for improvement for a block of 3-4 weeks.
There's so much that should be said about this, that an entire book could be written on the subject. And, many have been. However, I have a couple things I need to do right now. I'll try to revisit this thread later this evening.