Working around themes is a useful approach for higher level students. It also works very well with teenagers who may be getting a more grammar-based approach in their high school. It's also a good approach to take with small children who don't benefit from a focus on grammar.
It's usually a good idea to take a theme as your basis when planning a series of lessons. Themes might be friendship, environmental issues, families etc. This makes it easier to link activities than if you focus on language.
Try to find at least one activity for each of the 4 skills (reading, writing, listening and speaking) that link to this theme. Then think about which language points - grammar, vocab, functions and pronunciation - naturally occur when dscussing the theme at the level you are targeting.
Then look at how the different elements fit together. Aim to get variety and balance in each lesson. You should also think about sequencing; for example, presenting language points earlier in the sequence than speaking and writing activities where they will be used. Also plan in review sections; for example, language presented in the first lesson can be reviewed in the third or fourth.
Also consider the time of day and levels of energy for when you are with the students. Do more difficult activities when you think they'll have more energy. Lastly, remember ESA - engage, study, activate - for more on this, you can see my answer about ESA.