Loads of people who post on here just get the default response, "Wireshark it". I've used Wireshark lots, but it wasn't until I did a Wireshark course (witht hose nice chaps Fast Lane in London) that I realised I used it for about 1% of it's capabilities.
Now, together with tshark (to filter down massive PCAP files) I have some many more uses for it.
Anyway, GNS3 posted this on LinkedIn, hopefully may be of interest to someone on here
http://academy.gns3.com/courses/wireshark-the-art-of-sniffing
Use the coupon JAWS for a 50% discount.
I would also recommend CBT Nuggets courses if you really are interested in learning how to use Wiresharkhttps://www.cbtnuggets.com/it-training/wireshark-training-videos
And also, and of course, the Wireshark University http://www.wiresharktraining.com/.
They have a great book section with lots of Labs in, buy...