The English language has an exhaustive list of phrasal verbs, i.e. verbs that are necessarily accompanied by a preposition, without which they cease to be complete.
Most often there is a tendency to either drop out the preposition or use an inappropriate one. In fact the meaning can completely change if a phrasal verb is used out of context or incorrectly.
A popular anecdote goes that a teacher was pulled up when he asked the students to be quiet, since the Principal was passing away (meaning dying), when he was actually passing by.
So too every verb followed by a preposition is not a phrasal verb. For example, 'She accidentally came across the quote, she had been seeking, for a long time.'
Note the use of 'come across' as a phrasal verb, while in case of 'seek' despite it being followed by the preposition 'for', the two words do not constitute a phrasal verb. So too, the meaning would completely change, if one were to use 'come by' rather than 'come across'.
For example, 'I came across a good piece of writing, which is hard to come by these days'.
Other typically used phrasal verbs include 'run into', 'stand for', 'stand by', 'look into', 'look for', 'feel for', 'look down upon', 'look through', 'go in for', 'win over', 'look forward to', 'feel for', 'get through', 'get at', 'get even with'.
For example :
When the boss failed to look into the matter, he was looked down upon by his subordinates, who began to look through him, as they had nothing to look forward towhen it came to his role as a leader of the organisation; and so, the more talented from among them began to look for other opportunities.
She stood by him, when all that he stood for was questioned by those who failed to feel forthe cause.