If you immigrate to Canada under CEC, you will be assessed through the Express Entry system. This means that you will be assigned a score based on your and your spouse's (if any) age, education, English / French proficiency, work experience, availability of a job offer (it is not mandatory) and many other factors.
You must have worked in Canada for at least one year in the last three years before you apply. This can be a full-time work or an equal amount in part-time work. Self-employment and work while being a student do not count. The work must have been a managerial one (skill level 0), a professional one (skill type A), or a technical one or one in skilled trades (skill type B).
If your job was in skill level 0 or skill type A, you must have a knowledge of either English or French at what's known in Canada as CLB Level 7. Let's take IELTS General English test as an example. Your IELTS General test results must show at least the following numbers: Speaking - 6; Listening - 6; Reading - 6; Writing - 6.
If your job was in skill type B, you must have a knowledge of either English or French at what's known in Canada as CLB Level 5. Let's take IELTS General English test as an example. Your IELTS General test results must show at least the following numbers: Speaking - 5; Listening - 5; Reading - 4; Writing - 5.
Remember these are minimum scores, it's better if you have better results.
You do not have to complete an Educational Credential Assessment (ECA) of your foreign diplomas. However, it is advisable to raise your score if your score is below the passing mark. if you have Canadian education, you do not have to do an ECA.
You must be admissible to Canada. It means that your medical, criminal, financial, and political background must not have major problems. If you committed a crime, it does not mean you are ineligible. We will have to look into the details of your crime to advise you if you might overcome this inadmissibility.