5 Tips to Increase RSS Subscribers
The tips include:
1) Make it stand out
2) Offer a full feed
3) Subscriber count
4) Multiple buttons
5) Email Subscription
I agree with LiB that they are all good tips except for #3. I'm not big on subscriber counters either. If you have a high number of subscribers, it just seems like you're showing off. If your subscribers are few, it just looks sad.
But I can enthusiastically endorse the others, especially tip #5. Not every potential reader is into RSS so it makes tons of sense to offer an email subscription option also (it's really easy - check out FeedBlitz). More than half of those who subscribe to WisBlawg do so via email.