Actually, there's no easy way to do it, but it can be done.
First, you need to know the sites that promote your ads.
Go to your campaign profile -> Traffic sources -> Exclude from campaign (e.g. https://a-ads.com/campaigns/45372/ad_units). Here you can see a list of ad units that display your advertisement. Please, mind they are sorted like "probable sources of fake traffic first".
Then you click on any of them (e.g. ad unit 562131), look at its campaigns (https://a-ads.com/ad_units/562131/campaigns) and search through them. Here you can find your campaign and % of the ad unit traffic bought by your campaign:
You can check any other ad unit the same way. But you should understand the share of your campaign's traffic from this ad unit isn't constant.
Second, you should choose the ad unit where your campaign has the greatest traffic share and visit its site. Now you reload the site until you see your ad. That's all.