Side note: Selling vertical call and put spreads has been disappointing. Made money on them but nothing like the risk assumed to enter. Today made 3c off oct put vertical spread, idk hth this is possible, when I buy the damned things they just melt, today these held up really well and i just rage closed them, lol.
Selection of strikes and spread legs is critical IMO. The long leg should be pennies, really worthless, the purpose of it is to control your margin required. The short leg should be as much as you dare to get; optimally, selling ATM strikes yields the highest premium but also carries the greatest risk of exercise.
Never sell a spread for more than you can assume exercise. Once these get ITM you can be served notice of assignment at any time, very inconvenient, many horror stories.
Typically I sell a 30 to 60 day $15 spread ~$15 OTM. You can certainly make money off dailies on day of expiration but it's just picking up dimes in front of a speeding train IMO. If you short ten .25c puts and buy the .05c out contract on a $10 spread, you're risking $10,000 on margin to collect $200. I don't do dailies.