Eirik Westcoat's Viking Poetry for Heathen Rites includes a good how-to discussion at the beginning of the book on the different meters and what they were used for.
For the very basics, suitable to Old English/Anglo-Saxon poetry (there was much more variety recorded in Old Norse poetry than in Old English): 1) Each line is divided into two "half lines" with a caesura between them. Some authors render this as two separate lines, others with a large space at the caesura, and some with no visual indication at all. In speech in modern English, it usually works best as just barely a pause. These pairs of half-lines are the basic unit that the rules apply to. 2) Each half line must have two fully stressed syllables, but can include more unstressed syllables (minimum four syllables total) 3) The first stressed syllable of the second half line must alliterate with the first, second, or both stressed syllables of the first half-line in the pair 4) The second stressed syllable of the second half-line of the pair must not alliterate with the first stressed syllable in the second half-line, but may optionally alliterate with one of the stressed syllables in the first half-line 5) All vowels alliterate with each other 6) Consonant clusters that are spoken as one sound (like "sk", "sp", "th" and so forth) alliterate with themselves, not with the first letter (for example "skill" and "sketch" would alliterate, but "skill" would not alliterate with "sound")
If you're looking for some good examples, besides Westcoat's works (which also include some other Old Norse-inspired meters that have more complex rules, but with a core of "stress and alliteration"), Tolkien has some good stuff: his translation of Beowulf is mostly rendered in prose, but the book contains some poems composed in the style. His Legend of Sigurd and Gudrun is also entirely written in the very similar Norse meter called fornidhslag.
Lastly, not on the subject of meter, but if you are interested in constraining yourself to Germanic-derived words in Modern English, Plain English by Bryan Evans is a wonderful resource, as is the Anglish Moot wiki (https://anglish.fandom.com/wiki/Main_leaf). Certainly not a requirement, but I find it a fun creative constraint, and I enjoy the sound of Old Englishy words.
On the other hand, if you're looking to compose in Old English rather than modern English, Wordcraft by Stephen Pollington is rather helpful. It's mostly a brief dictionary, but it also includes thematic groupings of words, for example words that have to do with "starting" something or words that have to do with "thinking", so it also functions a bit like a thesaurus. Also, not on poetry specifically, but Pollington is my favorite writer on Anglo-Saxon history and religion, and I unreservedly recommend as many of his books as you can get a hold of.
Re: Eagle's Mead and Prayer Resources
For the very basics, suitable to Old English/Anglo-Saxon poetry (there was much more variety recorded in Old Norse poetry than in Old English):
1) Each line is divided into two "half lines" with a caesura between them. Some authors render this as two separate lines, others with a large space at the caesura, and some with no visual indication at all. In speech in modern English, it usually works best as just barely a pause. These pairs of half-lines are the basic unit that the rules apply to.
2) Each half line must have two fully stressed syllables, but can include more unstressed syllables (minimum four syllables total)
3) The first stressed syllable of the second half line must alliterate with the first, second, or both stressed syllables of the first half-line in the pair
4) The second stressed syllable of the second half-line of the pair must not alliterate with the first stressed syllable in the second half-line, but may optionally alliterate with one of the stressed syllables in the first half-line
5) All vowels alliterate with each other
6) Consonant clusters that are spoken as one sound (like "sk", "sp", "th" and so forth) alliterate with themselves, not with the first letter (for example "skill" and "sketch" would alliterate, but "skill" would not alliterate with "sound")
Here's what looks like a pretty decent discussion with plenty of footnotes if you want to explore further: https://people.uleth.ca/~daniel.odonnell/Tutorials/old-english-metre-a-brief-guide
If you're looking for some good examples, besides Westcoat's works (which also include some other Old Norse-inspired meters that have more complex rules, but with a core of "stress and alliteration"), Tolkien has some good stuff: his translation of Beowulf is mostly rendered in prose, but the book contains some poems composed in the style. His Legend of Sigurd and Gudrun is also entirely written in the very similar Norse meter called fornidhslag.
Lastly, not on the subject of meter, but if you are interested in constraining yourself to Germanic-derived words in Modern English, Plain English by Bryan Evans is a wonderful resource, as is the Anglish Moot wiki (https://anglish.fandom.com/wiki/Main_leaf). Certainly not a requirement, but I find it a fun creative constraint, and I enjoy the sound of Old Englishy words.
On the other hand, if you're looking to compose in Old English rather than modern English, Wordcraft by Stephen Pollington is rather helpful. It's mostly a brief dictionary, but it also includes thematic groupings of words, for example words that have to do with "starting" something or words that have to do with "thinking", so it also functions a bit like a thesaurus. Also, not on poetry specifically, but Pollington is my favorite writer on Anglo-Saxon history and religion, and I unreservedly recommend as many of his books as you can get a hold of.
Cheers,
Jeff