In German you can turn almost any verb into a noun with no ending at all. You take the infinitive, write it with a capital letter and give it the article das. lesen (to read) becomes das Lesen (reading), singen becomes das Singen, boxen becomes das Boxen. The gender is always neuter, whatever the verb means.
English speakers trip over this because English uses a different tool: the -ing form. It is tempting to guess a gender (der Lesen, die Reiten), to forget the capital letter, or to hunt for a German word ending in something like -ing. The simple mapping is this: an English activity noun in -ing is usually a German capitalized infinitive with das.
Three things always go together. The infinitive gets a capital letter, it takes das, and adjectives agree with it as a neuter noun (das laute Singen). To check whether you need the noun, ask whether an article, a preposition or an adjective stands in front of the word. If one does, it is a noun: zum Lernen, but Ich gehe lernen.
Because the noun is neuter, the everyday contractions beim (bei dem) and zum (zu dem) fit perfectly. beim + noun means while doing. zum + noun means for doing or to go and do.
Das Lesen macht mir Spaß.
(Reading is fun for me.)
Beim Essen spricht man nicht.
(One doesn't talk while eating.)
Mein Bruder geht zweimal pro Woche zum Boxen.
(My brother goes boxing twice a week.)
The words
Sports and hobbies
Here the -ing to infinitive mapping works almost perfectly: das Boxen, das Reiten, das Fechten, das Ringen, das Turnen, das Tauchen, das Fasten, das Singen, das Lesen, das Baden and das Programmieren. Verbs with a first element are written as one word: das Skifahren, das Skilaufen, das Eislaufen, das Schlittschuhlaufen, das Gewichtheben, das Seiltanzen, das Tauziehen, das Aufwärmen. Games work the same way: Verstecken spielen means to play hide and seek.
Im Winter fahren wir zum Skifahren in die Alpen.
(In winter we go skiing in the Alps.)
Nach dem Aufwärmen fängt das Training an.
(Training starts after the warm-up.)
Performing
English has one word, audition. German says what you do at the audition: das Vorsingen, das Vortanzen, das Vorsprechen.
Morgen habe ich ein Vorsingen an der Musikschule.
(Tomorrow I have an audition at the music school.)
Body and feelings
Sounds, faces and sensations: das Lachen, das Lächeln, das Grinsen, das Zwinkern, das Flüstern, das Schweigen, das Jucken, das Kitzeln, das Kribbeln, das Schlafwandeln, das Leiden. English often uses a plain noun here (a smile, silence), so the German neuter can surprise you.
Sie hat ein schönes Lächeln.
(She has a lovely smile.)
Everyday life and abstract ideas
das Fernsehen, das Herunterladen, das Nachdenken, das Handeln, das Verhalten, das Benehmen, das Aussehen, das Fehlen, das Verschwinden, das Bestehen, das Aussterben, das Überleben.
Beim Fernsehen schläft mein Vater immer ein.
(My father always falls asleep while watching TV.)
Nach langem Nachdenken hat er Ja gesagt.
(After a lot of thought, he said yes.)
Watch out
Some of these nouns have grown a meaning of their own, beyond the activity. They are still neuter. das Essen is both eating and food or a meal. das Leben is life, das Versprechen is a promise, das Vertrauen is trust, and das Vergnügen is pleasure. These nouns can have plurals. The plural looks like the singular: die Versprechen, die Leben. The pure activity nouns such as das Lesen have no plural.
Das Essen ist schon kalt.
(The food is already cold.)
Sie hat ihr Versprechen gehalten.
(She kept her promise.)
Das Leben in München ist teuer.
(Life in Munich is expensive.)
A typical mistake is copying English I like reading as Ich mag Lesen. That sentence is possible, but Germans usually say Ich lese gern. Use the noun when it is the subject, or after an article or a preposition. The same pattern gives you many more words, such as das Rauchen (smoking) and das Schwimmen (swimming).
Summary
If English uses an -ing noun for an activity, German usually takes the infinitive, capitalizes it and adds das: das Lesen, das Reiten, das Skifahren. The gender is always neuter, so beim (while doing) and zum (for doing) fit naturally. Some of these nouns also have a concrete meaning, like das Essen (food) or das Versprechen (promise), but they stay neuter.
Capitalized infinitives are always neuter nouns