Hi, I'm new to this too. I test every morning without fail before eating anything. Then I test just before a meal, and 2 hours after. I don't test after every meal now - if my fasting one was high then I test after breakfast, but I have the same thing for breakfast every day, and then do the same journey so whilst it can vary a little - I'm confident that what I'm eating is okay.
I test every time I eat something 'new' ie this week I had my first potatoes in 5 weeks (roast). I know that the portion I had and the fact I went on my exercise bike after dinner made it ok to eat them. I will test them again if/when I next have potatoes. I test the 'new' foods 2 or 3 times to see if it fluctuates alot. I work in an office so I now know that what I take to work the portions/the snacks are right for the amount of energy I am using.
This week I have been testing more as I have been unwell, and my boss understands if I say I need to go for a walk (her mother has diabetes), so when I had a couple of spikes I was able to get them back under control (when I say spikes it was 7.9 - which gives me a headache).
Hope this helps - I've also had to learn to eat more regularly - if I use too much/leave a longer gap between eating then my bloods seem to go up (the liver releases sugar if it thinks you are too low). I'm not an expert - but have read what the nurse gave me, plus all the advise from the great people on here. Good luck.