Also if you are getting a lot of traffic, a CDN is a good investment. CloudFlare.com is free. Others are around $20/month.
Finally, we encounter a lot of clients who come to us complaining their sites are loading slowly. Using something like tools.pingdom.com you might be able to tell if there is a giant image file that is slowing everything down. Also, some themes (free and premium) are not optimized well and load jquery 6 times, etc, which will slow down the page speed in a big way.
Finally, and I hate to rag on them all the time, but GoDaddy's hosting is painfully slow and can barely be helped. Move your site if you are on their servers.