Split the sentence into two (or more) separate sentences. End each sentence with a full stop (a "period", in American English), and start each sentence with a capital letter.
Alternatively, if the two component sentences are related, such that the second sentence is dependent on the first sentence in some way, they can be joined in a valid way using a semi-colon (";") or a colon (":"). In this case, the second part does not begin with a capital letter.
For example, this is a run-on sentence:
Run-on sentences are bad English, people who write them should be ashamed of themselves.
This is really two sentences strung together. You could write them as such, with a full stop and a capital letter:
Run-on sentences are bad English. People who write them should be ashamed of themselves.
Alternatively, since the second sentence is really just a follow-up to the first, it makes sense to link them with a semi-colon:
Run-on sentences are bad English; people who write them should be ashamed of themselves.
It's really just 2 separate sentences. We went to my cousin's wedding. Over 300 people were invited.
Put .
Yes, it is, in all grammatical ways a sentence.
It is correct where you put it.
To fix the run-on sentence, you can separate it into two sentences: "Rajeet opened the window. He loved the smell of a rainstorm."
There are different ways to write this sentence. The best way to write it would be "What were you doing before this"?
"How are you" is a correct sentence.
Yes, this sentence is correct.
You are palpitating. This is a correct sentence.
No, this sentence is not correct. It contains a hanging participle: 'Naming each picture' is not linked to the subject of the sentence. You could recast the sentence in various ways. Here is one example: 'Name each picture, and make a note of which names begin with the 'you' sound.'
With the exception of not capitalizing the 'y' at the start of the sentence, it is a correct sentence.
That sentence is grammatically correct.