The V2 rule states that in a Dutch main clause the finite conjugated verb must always occupy the second position, regardless of what occupies the first position. If the subject comes first, the order is Subject-Verb-Rest: Ik drink koffie. But if an adverb, object or subordinate clause moves to the first position, the verb still stays second and the subject is pushed after it — a process called inversion: Morgen drink ik koffie. Gisteren heeft zij gebeld.
This inversion is not optional. Dutch speakers perform it automatically. Common first-position elements include time adverbs like morgen and gisteren, place adverbs like hier and daar, conjunctive adverbs like dus and dan, and fronted objects or clauses: Het boek heb ik al gelezen. Omdat hij ziek was, bleef hij thuis — notice the main clause verb bleef immediately follows the comma after the fronted subordinate clause.
The V2 rule helps you predict word order in complex sentences. Whenever you start a sentence with anything other than the subject, expect the subject to follow the verb. This also explains why subordinating conjunctions like omdat, dat and als send the verb to the end — those clauses are embedded and the V2 rule applies only to the main clause. Practise by taking simple sentences and moving time or place expressions to the front, then adjusting the verb position accordingly.