I'd advise you to try formulating sentences in Russian which contain new words or just words difficult for you to remember. If it is possible, say the sentences aloud in order to practise your pronunciation (however, I don't think it's a good idea to do that while walking in the street since people around you would be surprised
). Create 3-5 sentences with a particular word or expression. Do the activity about half an hour or an hour a day, and that will help your brain to get used to speaking Russian. I guess this kind of practice and practice in general is especially helpful for training in applying the Russian cases.
I do such stuff with English, and I feel that it makes me better understand the usage of English words and expressions and just allows me to word my thoughts faster.
Speaking Russian with other people is very similar to the mentioned formulating activity but in this case it will be more complicated to practise new and difficult words mainly.
So I think combination of the formulating activity and speaking will do the trick. Besides don't forget about grammar if you have problems with it.