Not only cook your food in a cast iron pot but make enough of a tomato based dish for 2 days and leave the other half in the pot overnight. The acids in the toms leech small amounts of iron into your food. However, rhubarb and spinach are not good for overnighting in a cast iron pot - I think their acids bind to the iron but in a way that stops it being bioavailable .
Whatever your source of iron, take a source of Vit C with it - easiest being a glass of fresh orange juice with your meal, for example.
Lastly, try not to have a dairy protein meal with an iron rich protein meal, eg. beans, dark green leafys and orange juice for one main meal and cheesey omlette at another rather than a spinach omlette and cheesy beans. AFAIR, calcium/mag tends to get absorbed at the expense of iron.
I know a girl who mainly based her veggie meals on cheese and eggs and became severly anaemic.
Also, avoid tea and coffee with the iron rich meals. Nearly forgot!
Tbh I wouldn't be sure about your switching to a 100% vegetarian diet at least until yer well after the pregnancy and breast feeding stage, but even then I'd think about it carefully first. A little bit of good organic meat is a very important source of nutrition for some people and this might be the case for you if your diet is trstricted in other ways are you're not fond of beans etc..
Like Thoushaltnot mentioned don't use calcium supplements or dairy at the same time as you eat your iron rich meals.