How do I know when my veg is ready?

[hjscho]

I am sure from the 'subject' you can guess that this is my first year planting veg. I am just not sure how I know when things like raddishes, potatoes, beetroot are ready. In fact, even my salad leaves are foxing me, as I dont know how big they will get and whether I should wait longer or not. Any tips or suggested good reads to help me out on this one?

beetroots/radishes tend to be seen from above IYSWIM , like the top part of the veg?

Salad leaves you can pick when you want, 'cut and come again' type thing?

Potatos -no idea as I tend to leave them for my Dad to sort out and e tells me which are ready for digging

Potatoes is when the leaves start to dye back.

Best tip i found was checking out the fresh veg at my local farmers market !
I was like oh thats how long my beet leaves will grow ect .
Lettuces are a mystery.We have eaten half of them this weekend and left half to see what happens