Expect that a job application will contain some variation of a question based on finding out why you left your previous job. Decades ago, when employees tended to stay with one company for a longer length of time, the reasons were usually you got fired, you're moving, or the company went out of business. In today's world, plenty of acceptable reasons can explain why you left a job, but you should plan how to answer if you were fired from your last job.
Do not lie about why you left your previous job either during the interview or on your application. You could be fired for this years down the road if they find out you lied. Tempting as a lie might be, especially if your previous employment ended under acrimonious conditions, stick to the truth. Telling the truth doesn't preclude you from casting the circumstances in the most favourable light.
Certain phrases such as "quit," "got fired," or "laid off" simply do not sound good. Avoid using these as reasons for leaving your job. You have better ways to say the same thing. Instead of "fired," say you were "involuntarily separated" or "resigned," though you should check with your former employer to make sure they support that wording. Instead of "quit," say you "voluntarily separated" or "resigned." Be prepared to follow up with a good explanation of why you quit. Being laid off is not a shameful condition, but a phrase such as "lack of work" or "company downsizing" sounds and reads better.
The truth is that, unless you want to omit your time spent working at a job completely, what a previous employer has to say about the circumstances of your separation can have a big effect on landing a new job. As uncomfortable as it might be, that would be a good time to call your old boss and have an adult talk, expressing how important it is to have him tell a prospective employer you resigned. In most cases, he will agree to this.
Now that you have your old boss on board with the fact that you "resigned," it gives you much more leeway when it comes to answering the question about previous employment. Your resignation could have been to pursue career growth opportunities or to find a more challenging position. Maybe the workplace was too far away or you wanted to pursue educational opportunities.