Confused about basics of Greek

Confused about basics of Greek

I'm teaching myself Greek. I'm using William Mounce's "Basicsof Biblical Greek". He saysit'simperative (and I agree) to learn the stem of each word (Logos, stem is logo).

My problem: how do you get the stem? I mean, if the word Logo is the stem, that's cool, because there's no nominative, genetive, dative, or accusative case ending of omicron. But what about a word like kardia? Is the stem kardi? Or anthropos. Is the stem anthropo? The vocab in the book has anthropos, but that's nominative singular masculine, and accusative plural feminine? So to get to the stem, do I just take off all the leters until I get to a letter that's not a case ending? The book also has pro-phey-teys as the vocab. eta-sigma is not a case ending, but sigma is. And when I take sigma off, it leaves me with eta, which is also a case ending. Is doxa simply dox, since a is the nominative and accusative nueter plural ending? If I'mworng, and doxa is the stem, than how would I show it in the nominative/accusative nueter plural?

Can you tell I'm confused?

And here, actually, is were it gets me really stuck-
the book says that the stem for logos is logo, but for parsing it says the lexical form is the nominative singular, which would be logos. So is the lexical form ALWAYS the nominative singular and not the stem? If so, then how do I get to the stem (first paragraph question)? And why would the lecial form not be the stem?

I guess my main question is this- how do I find the stem. I am only on chp 7 out of like 35, and have learned so far only the alphabet and syllabification(sp?), and the nominative, geniitive, dative, and accusative case endings, and the article (first and second declension for these, not third yet). I can't just ignore learning how to get the stem as the book says you must learn the stems of words.
There is no short answer to your question but I have a suggestion.
The sites I found that give good answers to your questions have serious copyright statements, so I'll just tell you what I goggled to find them.
Google this: how to get the stem of an ancient greek word
You will find some good help there.