Please be reminded, I didn't read any materials from other sources, so my interpretation here might deviate from what been told in those reliable sources. So here it goes,
I think at the end of the season, Barney will get married and Ted will met 'Mother' at Barney's wedding.
Here is the reasons that I realizes;
Episode 1 - Ted is nervous (shown with the beer that given by Marshal). He either nervous about the wedding as the best man (and I think, it is Barney's wedding) and a girl that he might get interested with Ted is in that Church.
Episode 2 - Then, it follows with the story of Barney know a bout his real childhood's life. Plus with the possibility of finding his real dad (which at the end of the episode, is not his real father)
Episode 8 - In episode 8, there is one clue about Barney's father. The one with security guard about incredible accident's past few years back, during Barney's visit to the same Museum.
Episode 14 - In this episode Marshall's Father pass away. And this made Barney finally ready to meet up his dad.
Episode 16 - In this episode (last part of the episode), for the first time, Barney Stinson got a date on Valentine's day. (She is quite cute rite?)
Episode 18 - This episode is the most important episode to Barney's Stinson, in which he finally realize that he found out a woman that he can fall in love with and its suitable for him. But he have to let her go because of his 'rule'.
Episode 19 - Barney finally meet his dad and he is a bit disappointed with his dad because he walk out from his life since he is 10 years old.
Episode 21 - Barney's father try to make up with Barney. At the final part of the episode, Barney's father gives hint/tips about how to settle down, which is 'Have to meet the right girl'. And Barney said that 'Maybe, I meet her already' which reflect to his date in episode 16 and 18.
Episode 23 - And finally Zoey break up with Ted. Now Ted is single.
Currently, this week it is Episode 23 showing.
Er, wait a minute. The wedding in the first episode is might not Barney's wedding. It is possibly Ted's best friends wedding, in Episode 9, he ask Ted to be his best man. Well, it just my own prediction. Hope, we will meet 'Mother' soon.
Updated Episode 24: I think my first predictions about Barney's wedding will be came reality. Huwaaaa.