What to look for in surf forecasts to figure out good surfing conditions?

I've only been able to go for a surf 3 times because the conditions have been so good according to the forecasters notes. I'm using the website swellnet.com but I'm starting to think it's rigged because the conditions have been crap for the last few weeks except when I'm at work. I REALLY want to have another go at surfing and hopefully stand up this time.

How do you guys work out whether or not surfing conditions are good? I went once after I had a go at interpreting the results myself and found it crap. I thought that 2-3 ft swells at 5 second intervals would mean that I'd get plenty of practice since the wave period was so small. Spent hours driving there only to find out I was wrong. I spoke to the life guards and the people at the surf shops who told me that longer intervals are meant to be better. However the last few days when I've checked the forecast on the above website, they say there are 3-4 ft swells at 12 second intervals but they still rate it 2/10. Could someone explain what other information I'm missing?

Edit: TL;DR: the title is sufficient. I just began to rant and show off my kookiness in the description because I need help. Plus if anyone has advice or stories on how they made friends surfing that would be much appreciated.