Note that the gender of most first declension nouns is feminine. There are a few exceptions, such as poeta (poet),  pirata (pirate), agricola (farmer), incola (inhabitant) and nauta (sailor), best remembered by the acronym P-PAIN. These are masculine.

                                        SINGULAR                         PLURAL

NOMINATIVE         insulA                         insulAE

GENITIVE               insulAE                       insulARUM

DATIVE                   insulAE                       insulIS

ACCUSATIVE         insulAM                     insulAS

ABLATIVE               insulA                         insulIS

Note: The-a in ablative singular is long.

NOUNS OF SECOND DECLENSION (M)

NOMINATIVE         dominUS                     dominI

GENITIVE               dominI                         dominORUM

DATIVE                   dominO                        dominIS

ACCUSATIVE         dominUM                     dominOS

ABLATIVE               dominO                       dominIS

NB: There are some nouns in this declension which have a nominative singular in -er: ager (field) or puer (boy). Some have -ir (vir). Learn the genitive singular (agri, pueri, and viri, then simply interchange the other endings from dominus). The other endings are those you have just learned with dominus.

                                    SINGULAR                PLURAL

NOMINATIVE            pueR                            puerI

GENITIVE                   puerI                            puerORUM

DATIVE                        puerO                          puerIS

ACCUSATIVE              puerUM                       puerOS

ABLATIVE                    puerO                          puerIS

NOMINATIVE         signUM                         signA

GENITIVE                signI                             signORUM

DATIVE                     signO                           signIS

ACCUSSATIVE         signUM                        signA

ABLATIVE                 signO                           signIS

Two things should be noted here. First, the endings are very close to those of dominus above. These declensions are like first cousins. Second, note that the endings for nominative and accusative are the same. This holds true for all neuter nouns.