I picked up the free brochure "Exploring Kaunas" at our hotel and found it extremly helpful.
It not only includes town and local transportation maps, but also lists tips about sights, restaurants, nightlife and shopping. Apart from that it provides some basic information about Lithuania and its local customs.
Exploring Kaunas: http://www.exploring.eu/
Other useful brochures and maps are available at the Tourist information in Kaunas. Their main office is located at Laisves aleja 36.
Tourist Information: http://visit.kaunas.lt/
The Baltic States are rapidly developing countries, therefore an up to date guidebook is very helpful.
I used the Lonely Planet Guide "Estonia, Latvia & Lithuania" which offers information for all budgets on what to see and do, and tips on dining and accomodation.
On my travels to East and Central Europe I always try to get myself the latest edition of the "In Your Pocket" guide. These guides are very up to date, provide useful maps and offer all sorts of practical information for independent travels. Most of the tips can also be found on their webpage.
Lithuania is the cradle of "In Your Pocket" as the the first guide was published in Vilnius in 1991.
The Kaunas guide also includes information about Birstonas, Druskininkai, Kedainiai and Rumsiskes.
Miscellaneous: I found inyourpocket guides excellent value. You can buy them locally at a small price. If you just visit Kaunas and say Vilnius you may be better off just buying those guide booklet instead of lugging around a heavy guidebook. They also contain a town map and a small map of the country. You can order them online before you leave home if you want.
Miscellaneous: Not too many Lithuanians of older generation speak English, so it would be much easier for you to carry a mini dictionary. Although the youth is much more easier to converse with. Well, but just in case...
Luggage and bags: I think that you can find almost everything you need here in Kaunas, so you don't need to bring all your things with you. Of course, if you need something extra or special, then maybe it'll be better to take it with you.
Luggage and bags:
For walking around Kaunas, small, city backpack and surely bag for your camera - both water-proof.
Clothing/Shoes/Weather Gear: Comfortable walking shoes preferrably water-resistant: like good trainers or better special walking shoes (one example: Danish Ecco are very comfortable and... expensive but worth the cost).
Sun-glasses esp. in winter and summer and always a rain coat, eventually less comfortable umbrella.
Read info on climate in Lithuania:
Climate of Lithuania
Average temperatures and rainfall in Kaunas:
Check weather (10-day forecast) for Vilnius:
Weather forecast for Vilnius
Photo Equipment: Take as many films as you can or as large memory card as you can - Kaunas offers a lot for photography lovers :-). For pictures at night and/or bad light (weather) take a tripod.
Miscellaneous: Do not forget to take BIG SMILE :-) Enjoy!
There is no special rainy season
Avg. Temp. in Spring: max.: 3 – 18°C ( 38 - 64°F ); min: -1 - 9°C ( 30 - 49°F )
Avg. Temp. in Summer: max.: 19 – 22°C ( 66 - 73°F ); min: 10 - 13°C ( 50 - 55°F )
Avg. Temp. in Autumn: max.: 3 – 15°C ( 37 - 59°F); min: 0 - 8°C ( 32 – 47°F )
Avg. Temp. in Winter: max.: 0 – 2°C ( 32 - 36°F); min: -5 - 0°C ( 23 - 32°F )
Miscellaneous: In Kaunas and in Lithuania these days you can find various things you need, so you definitely don't have to bring your home with you. But take care about any special medicine you need because this can be hard to find.
Clothing/Shoes/Weather Gear: If you visit from November to March, be aware that it rains a lot in these months, with intermittent periods of heavy snow and extreme cold. Russians claim to recognize people from the Baltic States because they don't wear hats in the winter - and it's usually true! Western visitors should take the Russians' advice and put a warm hat on.
Miscellaneous: Before you set off on your Lithuanian trip I recommend buying a guide book or borrow one in your library. I found the Bradt in English language and the Reise Knowhow in German language very helpful.
a warm jacket or shirt is a must, cuz you never know about the weather for sure.
Camping/Beach/Outdoor Gear: An umbrella should be #1 item in your bad. Lithuania is famous for non stop rain.