I've heard 1 1/2 to 2 pounds. But it varies per person. If you want to be cautious, stick to 1 pound.

I lost an average of 2 1/2 pounds per week for 3 months back in 2003, and maintained the 30 pound weight loss since, but I already had a good general food routine (mostly whole foods, not excessive snacking) so cutting down to 1500 calories was easy)

Here are the keys to habit change, as far as I understand them from working/studying 30 years as a psychologist:

1. Motivation. This is often overlooked. You may have an idea you want to lose weight, but if you think a bit about what is involved, and look honestly, you really don't have the motivation.

2. Support: This can be online, but best is in person. Still whatever you can get is enormously helpful. This includes both interpersonal support and a supportive environment (don't keep your favorite junk food at home!)

3. Planning, especially for obstacles. This is one people rarely do thoroughly enough. Before you start to make ANY habit change, take at least a little time to look at how it's going to affect your life, and especially look at obstacles (does your employer keep junk food at work, particularly sweets that you love? Do you have friends that love to hang out at restaurants or cafes for hours eating desserts)

4. Easy, brief, baby steps, that build on what you already do. Have food available, learn to prepare simple foods (like a 2 minute microwave omelet, a 2 minute tortilla sandwich, etc, frozen foods if you like them) that are easy, and most important DELICIOUS.

5. Mindfulness - effortless, gentle, joyful, delightful. WAY too much to write about in a comment, but from what I'e seen, this may be more important than any other step: The ability to "be" with hunger pangs without having to act on them.