1) One of the easiest ways to quietly celebrate is to wear colours associated with the festival on the day. So for Litha, dig out your red, orange, yellow and green clothes!
2) Make a small gesture while you are out. It can mean sitting quietly for 10 minutes in the sun and appreciating the glory of its heat. Or it could be an act of giving to show your humble thanks - flowers for a friend, putting some money in a charity box.
3) Cook with traditional foods. So for Litha this will include honey, thyme or summer fruits.
4) Light a candle and aim to have some time for quiet contemplation in front of, or around, it. No one need know what you're thinking.
5) Break up rituals into smaller segments so that you fit in 5 minutes in the morning and say, 10 minutes later on in the evening.
6) Carry something with you all day, such as a Litha gemstone (anything yellow or green, tiger's eye and lapis lazuli), a pressed flower (or lavender), an amulet or a God or Goddess representation.
7) Generally have a bit of fun - especially for Litha! This is the time to connect with the fairies/faeries/fey and so a bit of mischievous giggling and laughter will conjure the right feel and tone.
8) A quick tarot reading can be very beneficial if you have cards with you. The energies are very often lively and open so even if you are not experienced you can get some great insight.
9) If you grew herbs such as mint or parsley at Ostara, make a small ritual out of cutting and using your successful yield. Yep, even I can grow mint!
10) Lastly, say a few words to yourself. They can be in the style of an incantation, something self-affirming that you intend to do over the next few months or something between you and the divine Gods and Goddesses. As long as it's meaningful to you, it will be altering the energies around you in a positive way and will make the difference.