If Search form is very important part of your site, you may want to highlight it in header and make much more big
For this. Go to theme option – general – custom css and add next code
form.search-form [type="submit"]{height:40px; line-height:40px; padding: 0 16px} form.search-form input[type="text"]{padding-left:15px; height:40px} header .search{max-width:500px; width:100% !important}
This will make search form in header bigger