So it's going to vary from state to state, but typically a warrant will be presented as a printed document on white paper. The may be a letter head or official symbol at the top.
As per the documents content, a Warrant should list the property that is to be searched, the evidence they expect to find (usually evidence of a specific crime), and any personal property they intended to seize for forensics lab work (Often this will be phones or computers, as they will run searches to test, but vehicles or even smaller items that could have been used in the crime will be seized as well.). It will also have the signature of the judge who authorized the warrant.
In most of the U.S. the organization delivering the warrant will either be the county Sheriff (usually a deputy, not the Sheriff themselves, in 47 states, the sheriff is the highest law enforcement officer in the county and while duties vary from county to county, almost all Sheriff's are responsible for enforcing the civil law of the state within their county (which 9/10 times, is enforcing what a judge says). 2 states do not have Sheriff's, Viriginia sheriff's have no jurisdiction in parts of their county that have a municipal police force so it gets weird. Additionally, most major cities with their own police forces might do the heavy lifting of the search while one single deputy hands you the paperwork) if it's a state crime (the vast majority of crimes in the U.S. are prosecuted by the state) or the FBI and/or some combination of federal law enforcement agencies AND/OR the U.S. Marshals (U.S. Marshals are the equivalent of the Sheriff in the Federal Courts, although usually they lack general investigation capability that the FBI, so if they bother to show up, it's just to be official. The Marshal's typical duties revolve around tracking fugitives, protection of federal court assets, and the witness protection program, so if they show up, you will probably be leaving with them.).
At either rate, if someone claims to be with any law enforcement organization and has a warrant, it's best to comply (again, unless it's a "no knock" they can read the warrant before you have to open up.).
Regardless, in the U.S. police must provide you with a copy of the warrant with little redaction (done for the purposes of preserving investigation integrity.). They must tell you the evidence they are searching for and the places they are authorized to search (If they search places they are not authorized to search, that's a warrantless search.). Additionally they can open up any containers in the searchable areas so long as it is reasonable that such a container could hold evidence they are searching for (so if they were looking for stolen Big Screen TV's and open up a sugar bowl and find Weed, which they weren't looking for, that weed isn't admissible, since you should know better than suspect a Big Screen TV is being hidden in a sugar bowl. They can still seize the weed, since it's contraband, but they can't use it as evidence for a possession charge. Do not argue about this, because those statements could be used against you for possession charges. Take the win).
Because each state (50), territory (5), district (1), and the federal government each have different court systems, there are easily 57 different formats the warrants can take, to say nothing of other special governments such as tribal reservations, some of which have their own independent court systems with the full authority akin to a state court system, it's best not to look for a clear identifying mark (Fun fact: The age old question of "if you kill a man on the four corners, who can prosecute, the answer is "all seven of them" since the four corner's monument marks the meeting point of four state borders, and sits on the border of two tribal reservations with full court systems and crosses state lines, which brings in the feds. You can be convicted for the same crime seven times because Double Jeopardy only applies to one court system trying you twice for the same crime. They might be a slight pause to determine if everyone can do something, since the actual marker may not be on the actual location of the four borders as it's poorly surveyed.).