First question I gotta ask is.....
Will this SWR meter be for a (100 watt) ham transceiver, or (5 watt) CB radio.....?
In either application you get what you pay for, you might get away with a 10 dollar meter for a stock CB, but if you need it for an amateur radio the meter shouldn't cost you any less than $60.00, and the better one's will run you closer to $150.00 or more. If you are running more than legal limit power through a CB, the same applies.
Second question.....
Was it a cross needle meter, or single needle meter.....?
With a cross needle arrangement there's no calabration required, but with a single needle meter you have to set the meter to "CAL" (calabrate) key the mic and adjust it so the needle sets to the calabration mark on the meter scale, then set the meter to SWR and key the mic again to determine what your SWR is.
The same "you get what you pay for" rule applies to your coax too, don't get me wrong here because I'm the king of cheap, but there is a difference between those pre made Radio Shack RG-8X jumpers, and one made with a good quality RG-213 or 9913 wire and Amphenol PL-259's.....
Disclaimer....
Not knowning what your level of expertise is with the radio hoby, I'am not trying to be insulting here, I'm trying to be helpful, so please don't take any of what I ask or say as an insult to your intelligence......