Search effects
Whenever a player searches through a deck, that player shuffles the deck after searching it unless a card effect says otherwise. Players do not shuffle or change the order of a discard pile after searching it.

That's in the game's official rule clarifications.

When I play a card like The Eagles Are Coming! I shuffle the player's deck after searching the top 5 cards for any number of Eagle cards (the card then only indicates to shuffle the other cards back...).
Some cards say "shuffle back into" like Eastern Crows or core Beorn , in these cases I don't shuffle the deck, I just put the card back somewhere.
It's evident that , when you "shuffle back into" without shuffling all the deck , that you know approximately where the card will be, and in some cases exactly where it is (for example if you shuffle back and there're 3 cards left in the deck).

It's really thin border between shuffle back into the deck and put the card where you want....

When I "shuffle back into" I always put the card somewhere in the middle of the deck ,but I'm tempted to put Beorn near the top and the crows near the bottom of their decks (if Thalin is not with me...), ahah! What about you?

When you are told to shuffle a card back into the deck you are supposed to shuffle the deck properly.

Thx, this takes me away from temptation.

The intent of "shuffle a card(s) back into your deck" is that the card could be located anywhere with equal probability, and that you don't have any idea where in the deck it is. I have seen few shuffles that truly deliver that, but if your not making a reasonable effort then you aren't really playing the game as its designed. I personally find it really hard to do the second bit properly by myself (ie not track where it probably is), so I usually get a friend to shuffle the deck for me.

Thx for clarifications ,
I played some of the earliest game in the wrong way before figuring out the right way, due to a non-clear trduction of the cards in my language. Now I'm fine and I'm thinking about buying an automatic card mixer

44 minutes ago, RichardPlunkett said:

The intent of "shuffle a card(s) back into your deck" is that the card could be located anywhere with equal probability, and that you don't have any idea where in the deck it is. I have seen few shuffles that truly deliver that, but if your not making a reasonable effort then you aren't really playing the game as its designed. I personally find it really hard to do the second bit properly by myself (ie not track where it probably is), so I usually get a friend to shuffle the deck for me.

When I try to know how to shuffle properly here is the feedback I got:

1- Riffle shuffle is king of the shuffle. Riffle shuffle mean that you take half of your deck and insert it on the other half. To get to a really clean situation 12 riffle seem needed. I was rarely courageous enough but doing 6 of it make a big effect;

2- Since this technic, in some conditions, an ability to know exactly where cards are (if cards are ABCDEFGH at the beginning they were AEBFCGDH after first riffle, then ACEGBDFH, then ABCDEFGH.. see the problem? ^^) it can be considered not to be real shuffle. I was doing some regular shuffle (overhand shuffle) to break the series every two riffle when I was playing Magic tournament and I keep that use since it break the problem that can occur with riffle shuffle.

On 10/20/2017 at 7:57 PM, Rouxxor said:

When I try to know how to shuffle properly here is the feedback I got:

1- Riffle shuffle is king of the shuffle. Riffle shuffle mean that you take half of your deck and insert it on the other half. To get to a really clean situation 12 riffle seem needed. I was rarely courageous enough but doing 6 of it make a big effect;

These numbers are somewhat overkill, I think.

The classic mathematical result is that 7 riffle shuffles of a traditional deck of cards is "good enough", but even that is overkill for LotR, since not only are our player/encounter decks usually fewer than 52 cards, but also there are many duplicates. Persi Diaconis helped update his original heuristic for this problem here:

https://arxiv.org/abs/0905.4698

In particular, the # of shuffles required to lose the position of a single card in a deck, if you are already ignorant of all the other cards' positions (a common situation in all card games), is usually quite low.

Personally, I tend to riffle shuffle things 4-5 times in LotR.

And be carefull that the Eagles don't fly away when riffle shuffling . Thx for commenting.

@sappidus Thanks for the additional explanation. 12 are supposed to give a full random from a full information state, in a 52 cards environement (where we are close at the beginning of the game). That why I said I tend to do between 4 and 7 riffle, with several (one to three) overhand shuffle at some point.