You will know (or not) by the orbits (which are elliptical) the distance between planets varies. Well, this year, the distance between Earth and Mars, during the months of April to September will be lower. Something that usually happens every approximately 14 years.
As the distance was/is so small, Mars can be distinguished by the naked eye (which also greater distances, but not for its distinctive reddish hue). And with binoculars until you can see the shape of the planet as it is only 56 million kilometers (being its greater distance 102 million kilometers).
The shortest distance is when the planet (planets, Earth and Mars) are in opposition, that is, when the Sun is in between Earth and Mars. The longest distance is when they are in conjunction, that is when the Earth that is in the middle.
But not only that, as the orbit is elliptical, there are two types of conjunctions, depending on whether the Sun is at the focus of the nearest or farthest ellipse. These are the perihelion and aphelion.