Notes, including links to thelatinlibrary.com's helpful handouts:
1st declension nouns are mostly feminine with a few exceptions (e.g. agricola, -ae, poeta,-ae); these exceptions still follow the same forms.
2nd declension nouns are mostly masculine or neuter with the exception of tree names, which are feminine (e.g. oak: quercus, -i); these follow the masculine forms. There are also a group of 2nd declension nouns with nominative forms that end in -r (e.g. vir, viri; ager, agri).
Most 3rd declension nouns follow the pattern shown in the chart, but a few nouns add an -i-before the ending in the genitive plural (all genders) and neuter nominative, accusative, and vocative plural, like the 3rd declension adjectives below.
4th declension nouns that end in -us are usually masculine, with a few exceptions.
There are relatively few 5th declension nouns, but they are mostly feminine, with the exception of dies, diei which is masculine, but can also be feminine.
Most adjectives fall into 2 categories
2-1-2 adjectives, e.g. calidus, calida, calidum or piger, pigra, pigrum
these are listed as masculine, feminine, neuter and follow all usual 2nd - 1st - 2nd declension rules
3rd declension adjectives decline mostly like 3rd declesion nouns, but use an -i in the ablative singular. See examples below
Masculine/feminine forms (ingens, ingentis) Neuter forms (ferox, ferocis)
Remember that adjectives modify nouns and use the same number, gender, and case as the noun they modify. But an adjectives does not need to match the declension of the noun! So, for example, ingens puer will see ingentem puerum in the accusative singular.