Students tend to work well when they are interested in a topic and when they feel they are learning something. For the oral activities in class, I suggest you find out what your students are interested in and then work on those areas. Speaking activities work best when you prepare students for what they are going to do. This means pre-teaching and practising any language structures and vocabulary that will be needed. It also entails giving students time to prepare what they are going to say.
You will increase the speaking time of each student if they work in pairs or groups rather than conducting a speaking activity as a whole class. After teaching and practising the language, and after giving students time to get their ideas together, put students into small groups or pairs. While they are speaking, go around and listen to what they are saying, help them where necessary without getting too involved in the discussion. Also, note down any errors they make and go over them at the end of the activity.
For a speaking exam, you could go away from the traditional one examiner and one student to create an exam where students are tested in pairs or groups. Put students together and give them a topic to discuss; while they are talking you can grade them on pronunciation, sentence structure and use of appropriate vocabulary. You could also mark them on what I like to call “communication aspects”. This is the ability to keep the conversation going within the group by asking classmates for their opinion, etc. It also involves managing a difficult situation; for example, when the student doesn’t know an item of vocabulary, can they improvise?
In a writing exam, you can test any or all of the following: grammar, vocabulary, sentence structure, punctuation, organisation of the essay and the ability to link ideas.
You could take a look at an FCE coursebook or exam book. They have very well structured exams and they will give you ideas for creating your own tests. FCE is aimed at intermediate level. If your students are not intermediate, you could look at another UCLES exam.
It is important that whatever you choose as a method for testing, that you explain this to the students beforehand and give them opportunities to practise this type of activity before the exam.