What John said.
Find out what their submission guidelines are.
Don't be fooled by the word guideline, they are rules and however great your submission may be, it will be most likely tossed immediately if you do not follow them.
If they do not have rules on their site check if they generally refuse submissions. If that is not the case find their contact information and ask them for their submission guidelines.
Some magazines belong together nowadays, like Elektor and circuit cellar, keep that also in mind.