The best season to visit Bali, is between April to October. It is called as dry season of Bali where you could witness heat, but evenings are cool. This time is called as Kite season in Bali that you get to witness lot of kites in the country.
Actually, you can visit Bali at any time, because Bali only has two seasons, the rainy season and the dry season.
Because most tourists want a vacation during the dry season in Bali, the level of tourist visits to Bali will increase. Both foreign tourists or Indonesian tourists. Months in Bali that have high tourist visits occur in June, July and August. it's better to come during the low season or often referred to as the low season, on the island of Bali it occurs in March, early April, September, October, November, early December.
The season that is most frequented by visitors is between April to September when the country doesn't receive rainfall and you can go around all the tourist attractions easily. But if you ask me, I would suggest go between October to March if you want to avoid crowd. Sure, you might encounter some rains and a bit of bad weather during your trip, but you will definitely enjoy the pristine beauty of the country when there are less tourists around. If weather does not bother you, this is the time for you! Also, the rates of accommodation, food and commuting are far less in the off season.
When you say - 'Good time to visit' it really depends on what you have in mind as the meaning of good time. Weather wise the best time in the summer (or the dry season as it is locally referred to) which is between April and October. However, during these months a lot of foreign tourists are visiting Bali, so the rates will be hiked up and the crowd will be huge. Whereas, during December-January, there might be less crowd as it is the peak of rainy season there. But the fields and pastures will be lush green during this time..
So, pick a season that suits your taste.. Happy traveling!