Algae growth can be attributed to 2 things generally. Too much light and/or excess nutrients in the tank.
So...
How long do you light the tank per day?
What are your water parameters?
Too much light is usually easy to address unless it gets sunlight. Reduce the time you leave the lights on, or shade the tank.
The excess nutrients are related to tank maintenance and stocking. A good regimen of regular PWC and vacuuming the substrate can aid this. Also a good running biofilter in the filter. An overcrowded tank will produce more nutrients than the biofilter can easily handle. These can be nitrates or phosphates.
Once in the tank, there will be a little more work involved to remove it, depending on the kind of algae present. Softer algae can be wiped or scraped off the glass and decor. Harder algae will need to be scraped or scrubbed off. Any algae that is cleaned will need to be removed from the tank, but some can remain if there are fish present who will eat it. There are also chemical solutions to remove algae, but I would steer clear of those unless absolutely necessary. Sometimes decor may need to be given a bleach dip, then scrubbed, cleaned and thoroughly rinsed.
So in summation, if you want to keep algae in check you have several options:
1) A healthy population of live plants will out-compete the algae for the available nutrients.
2) Algae eating fish, shrimp or snails will help keep it off of the decor and glass.
3) An external aquaponics setup will do the same job as plants in the aquarium.
4) Regular tank maintenance, PWC and a functioning, healthy biofilter are absolute requirements here.
5) Controlling the amount of light that the tank receives daily.
6) Chemical options... a last resort.
Hopefully this helps!