How to avoid customs charges from EU to UK?

How can I avoid customs charges from the EU to the UK or the USA to the UK?

Pay less for your items. One obvious way to avoid the charges is to always try and buy items worth under £135. ...
Break it down. Consider breaking down your order into two parts so you can keep the individual cost to under £135.

How much can I import without paying duty?

Mailing and Shipping Goods - Customs Duty Guidance Up to $1,600 in goods will be duty-free under your personal exemption if the merchandise is from an IP. Up to $800 in goods will be duty-free if it is from a CBI or Andean country. Any additional amount, up to $1,000, in goods will be dutiable at a flat rate (3%).