Is there a foolproof way of getting the right fit?

Am a little hesitant about a recent purchase. Bought a pair of slim fit low rise trousers from H&M. It fitted very well in the changing room.

That was then.

Tried it on this morning, and it looked a little "off". Maybe I need to test it over the weekend first before wearing it to work...

Which brings me back to the title. Are there ways to improve your chances of getting the right fit when you try it on in a store? I know for shoes, the usual advice is to shop for shoes in the afternoon, after our feet have swelled a little.

Circa 2012

This is so late; the annual dinner was in May, and I write about my outfit now.

Anyway, I decided on an outfit that looks like the one below.

The combi was

1. blue gingham shirt (new, from Uniqlo)
2. blue tie (SMA's very own)
3. light grey blazer (existing, G2000)
4. dark grey pants (existing, G2000)
5. dark brown oxford shoes (existing, Pedro)

I bought the same gingham shirt in black also, so if I'm lazy, I can use that for 2013. Use my dark grey suit, pair with black gingham shirt, and find a suitable tie. Tada.

"Variations on a Theme" - the light grey blazer

The annual dinner at my workplace is coming up again. Time to think about what to wear. 

Quick recap

2009 - black blazer, maroon striped shirt, black pants

2010 - light grey blazer, white shirt, black tie, dark grey pants

2011 - dark grey suit, black shirt, black tie

2012 - ???

Not so keen to buy another new suit, so I think I will start by going back to my light grey blazer.