A quick tip for checking data flowing through the Sitecore pipelines is to setup empty processors and then move them sequentially through the required pipeline.

An example for the pipeline:

using Sitecore.Pipelines.HttpRequest;

namespace ###.Domain.Cms.Specialization.Pipelines.HttpRequest
{
    public class PipelineDebugger : HttpRequestProcessor
    {
        public override void Process(HttpRequestArgs args)
        {

        }
    }
}

Then add your debug point and dig into the args.

Some example usage for checking which site has been resolved:

<processor type="Sitecore.Pipelines.HttpRequest.SiteResolver, Sitecore.Kernel" />
<processor type="###.Domain.Cms.Specialization.Pipelines.HttpRequest.PipelineDebugger, ###.Domain.Cms" />
<processor type="Sitecore.Pipelines.HttpRequest.UserResolver, Sitecore.Kernel" />