I think whatever you do, you need to pick a direction and stick with it, if only for continuity and at least until you know what works best for you.. For example, I originally started my YouTube account doing a few tutorials based on level design in video games.. This was great, but the views died off as everyone learned what to do, and people got stressed with level design or lost interest. In total, a 20 episode series got around 10k views. Not the best amount.
I then added a product review of something that wasn't reviewed in many other places. People are embedding the video on their eBay listings, on their online stores and blog sites etc. That's been up since Jan and has nearly got 7,000 views. So that worked better for me.
Then I moved on to minecraft. The views on these haven't been as good, and have been building VERY slowly. With so many Minecraft videos on YouTube, and massive competition from the Yogscast and others (and i mean massive! For a specific search term, they appear on the first 6 pages. I'm on page 7), it's actually really hard to get the views in.
So, I launched a series reviewing open source video games, and I think that's the key for me! I don't know how, but my two open source spotlight videos have exploded in views.. 13K the last time I checked and they've only been up 2 weeks.
It seems that finding that Niche is what it's all about. There's loads of videos about Minecraft, so I moved a little out of my comfort zone, and the views came in. Eventually if my subscribers increase, I'll get a little more traffic on my Minecraft videos, and so on and so on..
What am I trying to say then??
Basically, do what you love to do. There's no point making videos if you really don't enjoy doing them. If you love to vlog about stuff that annoys you, or vlog about your favourite foods then go for it
-- That's why your subscribers subscribed, so they'll probably enjoy hearing what you have to say. If you want to grow your audience a little more, try moving a little out of your comfort zone to do something similar to what you're doing now but give it a twist.
I like to play minecraft which is a video game, my subscribers liked that too. But I thought a good idea was to review another video game, my subs liked that too, and so did a bunch of new people.. Result: Keep subscribers AND increased views AND new subs.
You know what really seems to be in right now.... Lists of things and funny compilation vids with a bit of presentation in between. Maybe you could try doing your top 10 best funny clips, and talk a little bit about each one. But whatever you do, make sure you have fun and don't forget to have your audience interact.. "Leave me a comment with your favourite X and in a few weeks, we'll follow up with a list generated by you!"
Hope this makes sense (sorry, mad caffeine rush this morning.. Been up since 4!)
Dave