So, Jim over at the Daily Maybe is looking for things to boycott, and you can help him choose.
I've suggested religion, and I suppose that I had better elucidate. This is not the place to debate the whys and wherefores, but my case is that religion promotes bigotry, violence and deceit, that moderate religion is a sop that allows the extremists to thrive, and that the good points of religion are far outweighed by the bad ones. If you really want a theological argument then you can always rely on Ray Comfort, but I wouldn't recommend it unless you have an exceptionally thick skin.
So, assuming that you think a boycott is an appropriate response, what does that actually mean?
Firstly, a boycott implies giving up the outward trappings of religion including the church services for things like Christmas and Easter, weddings and funerals. Most weddings are now civil ceremonies, and humanist funerals are becoming more common, but if you are invited to a religious ceremony you can politely decline and offer to celebrate or pay your respects at the reception or wake (as appropriate).
The next element of any boycott is the economic one. Don't donate any money to churches or religiously run charities - find a secular alternative. Don't go to Church jumble sales or put money in collecting tins with checking how it is going to be spent. A more insidious form of religious revenue gathering is via the tax payer, with money going to faith based schools and other charities. The traditional form of protest against this is via petitions and letters to your mp, which probably won't have much of an impact in the short term but may well make a difference in the long run. Ultimately, it would be a good thing to see the disestablishment of the Church of England and the introduction of a purely secular constitution, although having said that, even the safeguards in the American constitution don't seem capable of keeping religion out of government.
Along the same lines, a political boycott means holding your mp or other representative to account if they vote according to the dictates of a particular religion, rather than in accordance with the wishes of their constituents. Ask them to declare their views, and whether they will keep them separate from their public actions. If they prefer to keep their religion private, then remind them that they can't have it both ways. If you have a choice, prefer an atheist candidate to a religious one.
Finally, banish religious thinking from your own life. Approach each problem and question with a degree of scepticism, and always look for evidence to back things up. Challenge your own beliefs, and never be afraid to change your mind (the privilege of the true skeptic). Challenge religious thinking where it intrudes into public life - for example, if you think that it is wrong to discriminate on the grounds of sexuality, why allow the religious an exemption on the grounds of something being a deeply held belief?