i haven't had any trouble with iron levels since i've been vegetarian, because i follow the advice above (get iron rich veggie foods, i particularly like figs, dried apricots, and beans and have some vitamin C--though you don't have to have them at the same time to gain the absorption, anytime during the day is fine), but i do not take supplements. i prefer to get what i need from food sources.
besides plant and meat sources, eggs and dairy can have a positive impact on your iron intake. eggs have 1 mg of iron per egg (RDA for women is 7-9 depending upon life cycle--menstrual, pregnant, lactating, menopausal). you won't need to eat 7 eggs, but a two egg breakfast plus your lentil soup at lunch, plus your salad, plus your citrus fruit should give you your RDA.
When transitioning to vegetarianism, it helps to have a good book on hand to answer your questions. There are lots of good ones out there--including many with recipes. YOu can also do a lot of research about vegetarian nutrition online--particularly for pregnant and lactating women that talks about these elements.
when it doubt, be sure to take your vitamins. When you get the hang of everything, then perhaps you can move away from vitamins or whatever.
give yourself time and don't worry about whether or not you eat dairy, eggs, or even meat right now. There is a lot to sort through--and i'd rather you start infromed and comfortable and can easily 'stick with it' than get started uneducated, get frightened, and then just head back to omnivore--you know?
i researched for 6 months before transitioning fully to vegetarianism, then another 3 months before going vegan. In the last 6 months or more, i've added eggs back into my diet for health reasons. But, the real key for me has been research and understanding my diet and how i function.
I wish you all the best!