On Fridays, on the Diwali night puja in the Pradosh or sthir lagna window, and at Sharad Purnima. Those keeping the Vaibhav Lakshmi vrat read it every Friday before breaking the fast.
What does the Chalisa actually ask for?
Read the second verse: gyan buddhi vidya do mohi - give me knowledge, intelligence and learning. Wealth comes later and is asked for as sukh-sampatti, settled well-being. The order of the requests is worth noticing.
Why is she called Sindhu suta?
Daughter of the ocean - she rose from the churning of the sea of milk. The name is used to place her beyond human contrivance: fortune is received, not manufactured, which is the attitude the Chalisa asks the reciter to hold.
What is offered to her?
Lotus or red flowers, kheer, kheel-batasha and white or kesar sweets, haldi and sindoor, a ghee lamp - and on Diwali the account books and coins placed before her. The Lakshmi puja samagri page has the list.
Should Ganesha be worshipped first?
Yes, that is the settled order at Diwali and on any Friday puja - Ganesh Chalisa or his mantra first, then Lakshmi. He clears the obstacles; she enters a house that is ready.
About the Lakshmi Chalisa
The Lakshmi Chalisa - the forty-verse hymn to Maa Mahalakshmi, goddess of wealth and fortune, recited for prosperity and well-being.
A chalisa is a devotional hymn of forty (chalis) verses (chaupais), framed by opening and closing dohas (couplets). The Lakshmi Chalisa above is given in both Hindi (Devanagari) and English (Hinglish, Roman script) so you can read it in whichever script you are most comfortable with - switch between the two using the buttons above. It is traditionally recited with devotion, often after a bath and before the deity, especially on the day associated with the deity.
A chalisa is forty verses. It is not the short lamp-song (that is an aarti) and not a longer Sanskrit stotram. Other forty-verse hymns are on the Chalisa index. For japa of a compact formula use a mantra. If you are keeping a fast, the story is under Vrat Katha.