AND = "A" when there is any type of contradictory or diiference between both parts:

• "I love you and you love him" - "Ja kocham ciebie a ty (kochasz) jego."
• "He cooks and she cleans the house" - "On gotuje a ona sprząta dom"
• "She is young and he is old" - "Ona jest młoda a on (jest) stary." (In the phrases containing contradiction, the repeated verb can be omitted). BUT: {@style=color: red} if the contradiction is not real, you only use different words to describe similar state, you go into nuances: "He is old and she is also not quite young" - "On jest stary a ona też niemłoda" (there is however some age difference between them, so she is younger than him) or "On jest stary i ona też niemłoda" (they are pretty similar, only you want to be polite and do not use the word "old" to describe a woman).
• "Her blouse is white and her skirt is red" - "Jej bluzka jest biała a jej spódnica (jest) czerwona." - it is so when the used verb is concerns the clothes itself, not the person who wears them; It works the same for longer lists: "Her hat is blue, her blouse is white, her skirt is red and her shoes are black" - "Jej kapelusz jest niebieski, bluzka biała, spódnica czerwona, a buty czarne." See also below.

AND = "I" when there is clear connection or similarity between both parts:

• "I love you and you love me" - "Ja kocham ciebie i ty kochasz mnie." (Attention, in this very case it would be also correct "Ja kocham ciebie a ty mnie", to underline sort of dualism: "you"-"me", while usage of i underlines the mutual similarity. With the usage of a, the repeated verb should be omitted).
• "He cooks and she cooks, too" - "On gotuje i ona też." or "On gotuje i ona też gotuje." or "On gotuje i ona gotuje."
• "She is young and he is young" - "Ona jest młoda i on jest młody."
• "Her blouse is white and her skirt is white" - "Jej bluzka jest biała i jej spódnica jest biała." or "Jej bluzka jest biała i jej spódnica też."
• BUT: when you enumerate the parts of clothing that somebody wears i.e. it is about the person, and not about the clothes, you rather use i no matter, whether they are similar or different (as there is no contradictory within the person itself, and the verb relates to the person, not the clothing): "She wears a white blouse and a white skirt" - "Ona nosi białą bluzkę i białą spódnicę."; "She wears a white blouse and a red skirt" - "Ona nosi białą bluzkę i czerwoną spódnicę."

I is when it means "+"
A is when there is a difference, something between "and " and "but"

The way it was explained to me and they way I understand is, if you use you could use either but or and in English without changing the meaning, then use a. If you can only use but, use ale. If only and, use i. It seems to work for me.

You use "a" when you want to oppose or confront things, for example: "That's a cat and that's a dog", "I wanted a small house and not a big one".

Sure thing, added.