In my experience to date, such signs only seem to turn up in times of crisis, unless I ask for one. I found a few feathers shortly after my mum died, but did not know about their significance then, but now look back and can see them for the signs that they were.
The latest one was when I was typing on this website. I was writing back to someone who had had a similar experience to me and I suddenly noticed a tiny white feather on the end of my finger. No feather cushions in here, no drafts that could have blown it in, yet there it was. I still feel it was there to say I was doing something good trying to help someone else upset and in a similar situation to me.
On the couple of occasions I have asked for a sign, that has worked for me too. You do feel rather silly talking to someone who has died in an empty room, but on the odd occasion I have felt in need of a sign and have asked for one, I have got it soon after, so it might be worth a try.
I had a low period a few weeks ago, when I felt very isolated and alone and just wanted a sign that my lost loved ones were still around. The next morning I was making a cup of tea and a robin flew into my conservatory and perched on the edge of a bowl for about three minutes and just looked at me, then flew away again. This had never happened before, nor has it happened again since. The night before, I had asked for a feather in my empty front room, just so I could be reassured I was not completely alone. I got more than a feather. I got a whole bird and I still feel that was my answer. It still bolsters me up now, several weeks later.
You need to be open-minded I think and not expect anything specific. But then something occurs and you recognise that this was your sign. Sounds unlikely, I know, but I believe in the things that have happened to me. Keep your eyes peeled, Thea. You may even have had some signs you haven't even recognised yet! I did.