You're probobly not going to be taking land as the Ottomans in a League War unless your League Leader decides to be very nice; so generally it boils down to two tactics:
1: If most of your enemies are in one League; join the opposite one to get a war against them where you have a lot of allies. This is particularly attractive if the League where your enemies are is the weaker one. You may not get land; but they can lose Emperor/Elector; miss out the 'X Empire' bonuses; get their manpower and money torn to shreds as they take a billion loans, and the AI leader may release nations/give land to others/any other number of things to screw with them as they separate peace
2: Stay out of it. Wait for the war to start. Jump in on your own later while the HRE/Europe is in complete turmoil and no-one will back anyone up due to loans/other wars/manpower.
Looking at who is in what Leauge; unless Muscovy is really strong [I can't see them fully] you should make claims on Italy/Austria and join the Protestants; because France; and Austria is pitiful. If Russia is stronger than you are, you should probobly stay out of it and declare separately later simply because you'd probobly end up having to 1v1 Russia; maybe with some Polish aid. The Protestants would still probobly win but you'd lose a lot of manpower/money and it might not be worth tangleing with Russia.
Also it's really rare that I see Russia join a League.