I am having 1 lookup field country. i want to set it with some default value on UI. How should i implement this?
One of the best solution is to use trigger. Create a insert trigger and set default value through that trigger.
Another solution is to pass the default value in the url. You have to get the id of that field and a URL can be created to set default value.
For eg. if the id of that field is 'country' , then url would be: https://ap1.salesforce.com/003/e?retURL=%2F003%2Fo&country=USA.
A new button can be created and URL on this button can be set to this one.