Like this (add some suggestions and additions in the comments however you want):

• "Hello" - Returns results with only the word "hello"
• "Hello World" - Returns results with only the phrase "hello world"

• case:on - enable case sensitive search

• community:<community@instance.com> - If instance.com is not provided, it returns the search results from a community from the current instance. Otherwise, it returns the community from the hosted instance: e.g: community:hello@sh.itjust.works
• instance:instance.com - returns results from a specific instance.
  • If instance:instance.com community:community, then search community from that specified instance.
• before:yyyy-mm-dd - Returns results from before a date.
• after:yyyy-mm-dd - Returns results from after a date.

• "-" before a phrase, keyword, community:community@instance.com, instance:instance.com, Excludes them from the results. Phrases like "hello world" should have the dash prefixed like this: -"hello world". Examples:
  • For words and phrases:
    • cyberpunk -2077 - Returns post/comments with the keyword "cyberpunk" but not "2077"
    • -"hello world" Removes posts/comments containing "hello world" from the search results
  • For communities: -community:hello, -community:hello_world@my.lemmy.instance
  • For instances: -instance:my.instance.com

About brackets in community:, instance:

• Used to select multiple communities and instances (separated with a comma or semicolon), for example
  • community:{philippines@lemmy.world,memes@lemmy.ml} hello -world - Returns search results only from communities philippines@lemmy.world and memes@lemmy.ml with the keyword "hello" and exclude world from post/comment results
  • -instance:{instance1.com,instance2.com,instance3.nft} community:{memes@lemmy.ml} hello -world - Exclude instances instance1.com, instance2.com, instance3.nft, show post/comments from community memes@lemmy.ml. Exclude posts/comments containing "world".

Here is my example usage:

Say you want to search memes@lemmy.ml for "hello world":

community:memes@lemmy.ml "hello world"

Shows results from memes@lemmy.ml with only the phrase "hello world"