In German, nouns can be in 3 genders- Masculine, Feminine, Neuter. The classification of nouns to different genders isn’t solely based on meaning (unfortunately), but there are some general rules which can be followed to identify the gender for a given noun (usually, and as always there are exceptions). Much of the stuff below I have taken from Gender of Nouns in German grammar

Masculine Nouns

Indicator Examples
Male People Mann, Präsident
Seasons of the year Frühling, Sommer, Herbst
Days Sonntag, Montag, Dienstag, Mittwoch....
Months Januar, Februar, März...
Nouns ending in 'er' / 'ling' Amerikaner, Lehrer, Schaffner, Vater, Schmetterling, Lehrling
Nouns that end in 'ich' or 'ig' Teppich, Honig
Nouns made from verbs without 'en' Lauf (from Laufen), Sitz (from Sitzen)
Types of Precipitation Regen, Schnee, Schauer

Feminine Nouns

Indicator Examples
Female People Frau, Präsidentin
Numbers used as nouns Eins
Nouns ending in 'in' / 'e' / 'heit' / 'keit' / 'ung' / 'schaft' / 'ion' / 'tät' / 'ik' Lehrerin, Sportlerin, Tasche, Straße, Schönheit, Freihiet, Wichligkeit, Freundschaft, Mannschaft, Hoffnung, Endung, Diskussion, Identität, Musik

Neuter Nouns

Indicator Examples
Letters of the alphabet das A
Nouns ending with 'chen'/ 'lein'/ 's'/ 'um'/ 'ment' Buchlein, Maüschen, Kindlein, Fräulein, Mädchen, Haus, Museum, Aquarium, Experiment, Thema , Drama
Nouns made from verbs in the infinitive Laufen, Essen
Nouns made from English verbs ending in 'ing' Timing, Training
Nouns that are made from adjectives that are not referring to something particular Neue, Ganze, Glesiche

A Few exceptions to these behaviours

  1. Mutter - Ends with ‘er’ but its a female person, and so it is feminine
  2. Fernster - Ends with ‘er’ but is a neuter

Note

In German nouns must always be capitalised.