I try to do something every day. On days where I booked a lesson I am doing up to 3 hours because I always prepare ahead of the lesson with either repeating what I´ve learned last time or doing my homework at the latest possible point :-). After intense learning days I always needs a break so I learn more if I do just a little, 30-60 min, every day. I get the best results when I am constantly confrontated with the target language, even if I do not really "study". E.g. I changed my facebook-app language to spanish. So every notification comes in spanish and my brain learns common vocabulary out of context.
I found an exchange partner and we text each other in my target language. Sometimes I start with english as it is much easier for me, but then I push myself to spanish. Even if I use Google translate, I am working with my target language and practise.
Also at work, none of my colleauges understand spanish but they get little notes from me in spanish. It´s kind of funny and an easy way for me to constantly use the language I learn without travelling to the country.