Make buttons look like a button
It is important that users can easily differentiate between a form field and a button. However, many forms do not make adequate distinction.
In fact, try to use standard OS form elements wherever possible. They may offend your designer sensibilities, however, the user is accustomed to using them and instinctively know what is required of them during this interaction.
Keep the look of all buttons consistent across the site.
Design
Designing a form is difficult. The best advice is to keep things as simple as possible and avoid introducing anything that will distract from the user’s primary goal: to complete the form. Use neutral colour palettes and provide plenty of space so the user can focus on the form, not on the page furniture.