There are many strict rules about how text is written but not about the placement of smileys. I wish there were some easy rules to follow so that we don't have to think too much.
These are the ways I often consider when I'm about to write a smiley:
The smiley is part of the sentence in a way so putting it before the dot makes perfect sense to me . It doesn't always look best this way though.
When having only one sentence in a paragraph I think it looks best to put the smiley after the dot. If there is a following sentence it looks a bit weird, as if the smiley was part of that sentence instead.
Replacing the dot works for a single sentences With multiple sentences it might not be obvious that the smiley is acting as a sentence terminator. Some people might have smileys within a sentence which makes it even less clear.
If I have to choose one of the above to use in all situations I would probably choose the first one (smiley before dot) but I'm not sure I should be so strict. What do you think?
I'd say after the dot.
I try to use smileys as sparingly as I can, unless I'm really celebrating something, then I use a whole row of them. I usually replace a dot with the smiley, as the smiley looks like a big smiling dot to me, and I also like to use a few dots leading up to the smiley, like this ....
When it comes to the other end-of-sentence characters ! and ?. I think it becomes extremely ugly when putting the smiley before because there is no space between the smiley and the end-of-sentence character. You could of course put an extra space in there but it doesn't look nice.
I do not think that there is a hard and fast rule on how or where to place smileys. It is not English grammar. You can put it before the full stop or after it. Skipping a full stop (.) can confuse a reader.
Personally I prefer to put a smiley before the dot .