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I have used Gildersleeve's Latin Grammar (B.L. Gildersleeve and G. Lodge, 1997: Bolchazy-Carducci) to aid my memory. I also used http://www.perseus.tufts.edu for verification.
One of the major, perhaps artificial divisions in declension in the Latin language.

Famed for notable regularity as opposed to third declension, the 2nd consists of mostly masculine and neuter words.

famulus, -i (masculine) slave, servant

This fairly common us, -i form is declined as follows:

Singular
nominative ----- famulus
genitive ------- famuli
dative---------- famulo
accusative ----- famulum
ablative ------- famulo

Plural
N. --------------- famuli
G. --------------- famulorum
D. --------------- famulis
Ac. -------------- famulos
Abl. ------------- famulis

Vocatives
S. --------------- famulum, rare e in other nouns (Gildersleeve)
P. --------------- famuli 


The second most common subcategory is the er, -i nouns.

puer, -i (masculine) usually "boy", infant through adolescent male

er, -i nouns differ only in their nominative singular -er ending puer and vocative singular -er (same).

Neuters are formed in a very regular manner as well.

templum, -i generic temple, sacred space (needn't be a building per se)

Same as standard us, -i except nominative and accusative singular are same. Plural nominative, accusative, and vocative end in -a, ie templa.

While city names generally cross declensional rules, according to Gildersleeve some Greek loanwords in the feminine are considered 2nd:

methodus, -i method

In my opinion as a (perhaps feeble) student of Latin the second declension is the second easiest to master (after the first declension.) The true test of declensional knowledge comes with familiarity with the third declension. There irregularity appears with much greater frequency, in a time when high school students already have enough stress.