Bit vague in the OP but I'll take it and run with it....
Job adverts without a listed salary - avoid like the plague. "Competitive salary" means fuck all and if they don't tell me how much the starting salary is, I'm not going to waste my time with what's usually an extensive and complex application process only to find out the salary is less than I'm currently on.
Jobs with no salary (0 hour contracts) - good and bad depending on the role. I was a 0 hour contract waitress at the age of 16-19 and it worked perfectly for me as it fit around my studies and I could request more or less weekly shifts, but my earnings varied massively on a weekly basis and the hours were not guaranteed. Shit for most people who have a mortgage/rent/bills/debts to pay on time unless the job and hours are secure.
I feel happiest in a salaried job. I know my hours, know my pay, it doesn't change and there are no unpleasant surprises. If I was going to apply for a different job, I wouldn't bother applying unless they state the salary. If it's as "competitive" as they say it is, stating the salary would only bring more/higher skilled applicants so I usually assume that if a salary isn't stated, it's because it's on the lower end of the scale that can be expected in that role.