The speaking skills required in international speaking exams can be quite daunting for candidates because many candidates have no idea what the examiners are looking for.
Let's take the IELTS speaking task for an example. The test begins with a few simple questions about yourself. He/she will ask you questions about your job or studies, what you are doing now, what your role or responsibilities and duties include. Here you are using a variety of present tenses.
He might ask about past employment or experiences therefore you will be using simple past or maybe past continuous.
He will then move to your future hopes and ambitions and once again you will be able to show your competence is using future tenses.
If you are not sure about how to form these there is an excellent Verb Tense tutorial in English Page
http://www.englishpage.com/verbpage/verbtenseintro.html Don't be afraid to go back to basics to brush up on grammar you have forgotten. Remember the exam is giving you a chance to show off your skills.
If you are not used to talking about yourself then write it down as an essay. look at example questions they might ask and write down short answers of one or two sentences, Read then aloud a few times, even record yourself to see how you sound.
If you would like to see videos of students practicing their skills go to. http://www.ipassielts.com/ielts_training/videos/speaking/ listen and also read the transcripts and more importantly the teacher feedback.
My next blog will be about the second task.